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  • Python point lookup (coordinate binning?)

    - by Rince
    Greetings, I am trying to bin an array of points (x, y) into an array of boxes [(x0, y0), (x1, y0), (x0, y1), (x1, y1)] (tuples are the corner points) So far I have the following routine: def isInside(self, point, x0, x1, y0, y1): pr1 = getProduct(point, (x0, y0), (x1, y0)) if pr1 >= 0: pr2 = getProduct(point, (x1, y0), (x1, y1)) if pr2 >= 0: pr3 = getProduct(point, (x1, y1), (x0, y1)) if pr3 >= 0: pr4 = getProduct(point, (x0, y1), (x0, y0)) if pr4 >= 0: return True return False def getProduct(origin, pointA, pointB): product = (pointA[0] - origin[0])*(pointB[1] - origin[1]) - (pointB[0] - origin[0])*(pointA[1] - origin[1]) return product Is there any better way then point-by-point lookup? Maybe some not-obvious numpy routine? Thank you!

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  • This query show me with this active record

    - by New Kid
    I am having trouble getting two tables and passing them to controller: IN A MODEL: function get_all_entries() { $query = $this->db->get('entry'); return $query->result(); $this->db->select('entry_id , count(comment_id) as total_comment'); $this->db->group_by('entry_id'); $comment = $this->db->get('comment'); return $comment->result(); } IN A CONTROLLER: $data['query'] = $this->blog_model->get_all_entries(); $this->load->view('blog/index',$data); How do I return $query and $comment variables to controller? I think I am doing it wrong.

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  • JQuery code problem?

    - by SLAPme
    New to JQuery, I added the following JQuery code below and moved it around in my code and now it won't work I forgot what I did, can someone fix my code by placing the below code in its correct place thanks. $('a').click(function () { $('#changes-saved').remove(); }); return false; // prevent normal submit }); JQuery code. $(function() { $('#changes-saved').hide(); $('.save-button').click(function() { $.post($('#contact-form').attr('action'), $('#contact-form').serialize(), function(html) { $('div.contact-info-form').html(html); $('#changes-saved').append('Changes saved!').show().pause(1000).hide(); }); return false; // prevent normal submit }); $('a').click(function () { $('#changes-saved').remove(); }); return false; // prevent normal submit }); });

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  • How to break closures in JavaScript

    - by Not a Name
    Is there any way to break a closure easily in JavaScript? The closest I have gotten is this: var src = 3; function foo () { return function () { return src; } } function bar (func) { var src = 9; return eval('('+func.toString()+')')(); // Line breaks closure } alert(bar(foo())); Which prints 9, instead of 3 as a closure would dictate. However, this approach seems kind of ugly to me, are there any better ways?

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  • How to determinate file in Perl

    - by rodnower
    Hello, I use File::Find - find(\&f, $directory) for find some file with some content. Relevant part of my delegate looks like: sub f { my $file = $File::Find::name; return unless -f $file; return unless $file =~ /$file_pattern/; etc... but the problem is that, that this code returns every time where $file not exist in current directory. For example for file ./test it fine, but for file ./dir/test this return... Is there some better way to know if $file is file?

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  • MySQL join not returning rows

    - by John
    I'm attempting to create an anti-bruteforcer for the login page on a website. Unfortunately, my query is not working as expected. I would like to test how many times an IP address has attempted to login, and also return the ID of the user for my next step in the login process. However, I'm having a problem with the query... for one thing, this would only return rows if it was the same user as they had been trying to login to before. I need it to be any user. Secondly, regardless of whether I use LEFT JOIN, RIGHT JOIN, INNER JOIN or JOIN, it will not return the user's ID unless there is a row for the user in login_attempts. SELECT COUNT(`la`.`id`), `u`.`id` FROM `users` AS `u` LEFT JOIN `login_attempts` AS `la` ON `u`.`id` = `la`.`user_id` WHERE `u`.`username` = 'admin' AND `la`.`ip_address` = '127.0.0.1' AND `la`.`timestamp` >= '1'

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  • Why does String.Equals(Object obj) check to see if this == null?

    - by m-y
    // Determines whether two strings match. [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)] public override bool Equals(Object obj) { //this is necessary to guard against reverse-pinvokes and //other callers who do not use the callvirt instruction if (this == null) throw new NullReferenceException(); String str = obj as String; if (str == null) return false; if (Object.ReferenceEquals(this, obj)) return true; return EqualsHelper(this, str); } The part I don't understand is the fact that it is checking for the current instance, this, against null. The comment is a bit confusing, so I was wondering what does that comment actually mean? Can anyone give an example of how this could break if that check was not there, and does this mean that I should also place that check in my classes?

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  • Constructors and method chaining in JavaScript

    - by Sethen Maleno
    I am trying to make method chaining work in conjunction with my constructors, but I am not exactly sure how to go about it. Here is my code thus far: function Points(one, two, three) { this.one = one; this.two = two; this.three = three; } Points.prototype = { add: function() { return this.result = this.one + this.two + this.three; }, multiply: function() { return this.result * 30; } } var some = new Points(1, 1, 1); console.log(some.add().multiply()); I am trying to call the multiply method on the return value of the add method. I know there is something obvious that I am not doing, but I am just not sure what it is. Any thoughts?

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  • Removing words from a file

    - by user1765792
    I'm trying to take a regular text file and remove words identified in a separate file (stopwords) containing the words to be removed separated by carriage returns ("\n"). Right now I'm converting both files into lists so that the elements of each list can be compared. I got this function to work, but it doesn't remove all of the words I have specified in the stopwords file. Any help is greatly appreciated. def elimstops(file_str): #takes as input a string for the stopwords file location stop_f = open(file_str, 'r') stopw = stop_f.read() stopw = stopw.split('\n') text_file = open('sample.txt') #Opens the file whose stop words will be eliminated prime = text_file.read() prime = prime.split(' ') #Splits the string into a list separated by a space tot_str = "" #total string i = 0 while i < (len(stopw)): if stopw[i] in prime: prime.remove(stopw[i]) #removes the stopword from the text else: pass i += 1 # Creates a new string from the compilation of list elements # with the stop words removed for v in prime: tot_str = tot_str + str(v) + " " return tot_str

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  • Prioritize SQL WHERE clause

    - by JaTochNietDan
    Basically I want to do this: SELECT * FROM `table` WHERE x = 'hello' OR x = 'bye' LIMIT 1'; I want it to return 1 value, but to prioritize results from the 1st where clause. So if there exists a row where column x's value is "hello", it will not return the result from the 'bye' value. If the "hello" value doesn't exist though, it will return the result from the 'bye' value. Can't figure out a way to do it even though it seems fairly trivial. Any ideas?

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  • Sum of a matrix, even or odd

    - by user1790201
    This function receives a numeric matrix represented as a list of rows, where each row is in turn a list. Assume that it is a square matrix: all rows have the same length and there are as many rows as elements in each row. Also assume that the matrix is at least of dimension 2 by 2 (i.e. minimally the matrix has 2 rows with 2 elements each) The function should return a list with as many elements as number of rows. Element i in the resulting list should have the sum of the values in row i. For example, if the matrix is 1 2 3 10 20 30 100 200 300 then this function should return the list [6,60,600] That is, addValuesInAllRows( [ [1,2,3], [10,20,30], [100,200,300] ] ) should return [6,60,600] Isn't this sort of similar but how would you sum up the list individually

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  • Is it possible in Java to implement something similar to Object.clone() ?

    - by devoured elysium
    The Object.clone() method in Java is pretty special, as instead of returning a copy of the object that is to be cloned with the Object type, it returns the correct Object type. This can be better described with the following code: class A extends Object { public A clone() { return super.clone(); //although Object.clone() is from the Object class //this super.clone() will return an A object! } } class B extends A { } public static void main(String[] args) { B = new B(); B.clone();//here, although we haven't defined a clone() method, the cloned //object return is of type B! } So, could anyone explain if possible if is there anyway to replicate what happens inside Object.clone()'s method?

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  • Which function should i use for testin if a var isset or not?

    - by streetparade
    I'm sometimes confused to using which one of them, say i have a function called getmember($id) function getmember($id) { // now this is the confusing part // how do i test if a $id was set or not set? //solution 1 if(empty($id)) { return false; } // solution 2 if(isset($id)) { return false; } } Thats sometimes not clear tome some times if a parameter in a function is set like function($var="") Then i do if($var ==="") { return false; } What should i use the next time isset ? emtyp ? or ===''

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  • How to determine if two strings are sufficiently close?

    - by A.06
    We say that we can "hop" from the word w1 to the word w2 if they are "sufficiently close". We define w2 to be sufficiently close to w1 if one of the following holds: w2 is obtained from w1 by deleting one letter. w2 is obtained from w1 by replacing one of the letters in w1 by some letter that appears to its right in w1 and which is also to its right in alphabetical order. I have no idea how to check if 2. is fulfilled. To check if 1. is possible this is my function: bool check1(string w1, string w2){ if(w2.length - w1.length != 1){ return false; } for(int i = 0,int j = 0;i < w2.length;i++;j++){ if(w2[i] == w1[j]){//do nothing } else if(i == j){ j++; } else{ return false; } } return true; } Given two words w1 and w2, how do we check if we can 'hop' from w1 to w2?

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  • MySQL Query Problem

    - by user559744
    Hello guys, I'm getting following error message. Please help me. Thanks Notice: Trying to get property of non-object in C:\xampp\htdocs\my\include\user_functions.php on line 34 Here is my Code $conn = db_connection(); if($conn == false) { user_error('Unable to connect to database'); return false; } $query = "UPDATE user SET passwd = '".$new_passwd."' WHERE username = '".$username."' "; $result=$conn->query($query); if($result == false) { user_error('Query Error'.$conn->error); return false; } if($result->num_rows == 1) { echo 'Password changed'; } else { echo 'Failed '; } here is my db_connection function db_connection() { $db = new mysqli('localhost','root','','php_login'); if(!$db) { echo 'Could not connect to database server'; } else { return $db; } }

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  • Learning Python Basics

    - by StaticExtasy
    So I'm trying to learn python better and i've been using this website http://www.learnpython.org/ I'm on to functions right now, heres the code #Add your functions here (before the existing functions) def list_benefits(): myList = ['More organized code','More readable code','Easier code reuse','Allowing programmers to share and connect code together'] return myList def build_sentence(info): addMe = " is a benefit of functions!" for i in info: meInfo = i + addMe return meInfo def name_the_benefits_of_functions(): list_of_benefits = list_benefits() for benefit in list_of_benefits: print build_sentence(benefit) name_the_benefits_of_functions() the output being e is a benefit of functions! e is a benefit of functions! e is a benefit of functions! r is a benefit of functions! What am i missing to return the whole scentence

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  • i am using winsock2.h in c language the following errors are unuderstandable help required?

    - by moon
    i am going to paste here my code an errors :::: #include "stdio.h" #include "winsock2.h" #define SIO_RCVALL _WSAIOW(IOC_VENDOR,1) //this removes the need of mstcpip.h void StartSniffing (SOCKET Sock); //This will sniff here and there void ProcessPacket (unsigned char* , int); //This will decide how to digest void PrintIpHeader (unsigned char* , int); void PrintUdpPacket (unsigned char* , int); void ConvertToHex (unsigned char* , unsigned int); void PrintData (unsigned char* , int); //IP Header Structure typedef struct ip_hdr { unsigned char ip_header_len:4; // 4-bit header length (in 32-bit words) normally=5 (Means 20 Bytes may be 24 also) unsigned char ip_version :4; // 4-bit IPv4 version unsigned char ip_tos; // IP type of service unsigned short ip_total_length; // Total length unsigned short ip_id; // Unique identifier unsigned char ip_frag_offset :5; // Fragment offset field unsigned char ip_more_fragment :1; unsigned char ip_dont_fragment :1; unsigned char ip_reserved_zero :1; unsigned char ip_frag_offset1; //fragment offset unsigned char ip_ttl; // Time to live unsigned char ip_protocol; // Protocol(TCP,UDP etc) unsigned short ip_checksum; // IP checksum unsigned int ip_srcaddr; // Source address unsigned int ip_destaddr; // Source address } IPV4_HDR; //UDP Header Structure typedef struct udp_hdr { unsigned short source_port; // Source port no. unsigned short dest_port; // Dest. port no. unsigned short udp_length; // Udp packet length unsigned short udp_checksum; // Udp checksum (optional) } UDP_HDR; //ICMP Header Structure typedef struct icmp_hdr { BYTE type; // ICMP Error type BYTE code; // Type sub code USHORT checksum; USHORT id; USHORT seq; } ICMP_HDR; FILE *logfile; int tcp=0,udp=0,icmp=0,others=0,igmp=0,total=0,i,j; struct sockaddr_in source,dest; char hex[2]; //Its free! IPV4_HDR *iphdr; UDP_HDR *udpheader; int main() { SOCKET sniffer; struct in_addr addr; int in; char hostname[100]; struct hostent *local; WSADATA wsa; //logfile=fopen("log.txt","w"); //if(logfile==NULL) printf("Unable to create file."); //Initialise Winsock printf("\nInitialising Winsock..."); if (WSAStartup(MAKEWORD(2,2), &wsa) != 0) { printf("WSAStartup() failed.\n"); return 1; } printf("Initialised"); //Create a RAW Socket printf("\nCreating RAW Socket..."); sniffer = socket(AF_INET, SOCK_RAW, IPPROTO_IP); if (sniffer == INVALID_SOCKET) { printf("Failed to create raw socket.\n"); return 1; } printf("Created."); //Retrive the local hostname if (gethostname(hostname, sizeof(hostname)) == SOCKET_ERROR) { printf("Error : %d",WSAGetLastError()); return 1; } printf("\nHost name : %s \n",hostname); //Retrive the available IPs of the local host local = gethostbyname(hostname); printf("\nAvailable Network Interfaces : \n"); if (local == NULL) { printf("Error : %d.\n",WSAGetLastError()); return 1; } for (i = 0; local->h_addr_list[i] != 0; ++i) { memcpy(&addr, local->h_addr_list[i], sizeof(struct in_addr)); printf("Interface Number : %d Address : %s\n",i,inet_ntoa(addr)); } printf("Enter the interface number you would like to sniff : "); scanf("%d",&in); memset(&dest, 0, sizeof(dest)); memcpy(&dest.sin_addr.s_addr,local->h_addr_list[in],sizeof(dest.sin_addr.s_addr)); dest.sin_family = AF_INET; dest.sin_port = 0; printf("\nBinding socket to local system and port 0 ..."); if (bind(sniffer,(struct sockaddr *)&dest,sizeof(dest)) == SOCKET_ERROR) { printf("bind(%s) failed.\n", inet_ntoa(addr)); return 1; } printf("Binding successful"); //Enable this socket with the power to sniff : SIO_RCVALL is the key Receive ALL ;) j=1; printf("\nSetting socket to sniff..."); if (WSAIoctl(sniffer, SIO_RCVALL,&j, sizeof(j), 0, 0,(LPDWORD)&in,0, 0) == SOCKET_ERROR) { printf("WSAIoctl() failed.\n"); return 1; } printf("Socket set."); //Begin printf("\nStarted Sniffing\n"); printf("Packet Capture Statistics...\n"); StartSniffing(sniffer); //Happy Sniffing //End closesocket(sniffer); WSACleanup(); return 0; } void StartSniffing(SOCKET sniffer) { unsigned char *Buffer = ( unsigned char *)malloc(65536); //Its Big! int mangobyte; if (Buffer == NULL) { printf("malloc() failed.\n"); return; } do { mangobyte = recvfrom(sniffer,(char *)Buffer,65536,0,0,0); //Eat as much as u can if(mangobyte > 0) ProcessPacket(Buffer, mangobyte); else printf( "recvfrom() failed.\n"); } while (mangobyte > 0); free(Buffer); } void ProcessPacket(unsigned char* Buffer, int Size) { iphdr = (IPV4_HDR *)Buffer; ++total; switch (iphdr->ip_protocol) //Check the Protocol and do accordingly... { case 1: //ICMP Protocol ++icmp; //PrintIcmpPacket(Buffer,Size); break; case 2: //IGMP Protocol ++igmp; break; case 6: //TCP Protocol ++tcp; //PrintTcpPacket(Buffer,Size); break; case 17: //UDP Protocol ++udp; PrintUdpPacket(Buffer,Size); break; default: //Some Other Protocol like ARP etc. ++others; break; } printf("TCP : %d UDP : %d ICMP : %d IGMP : %d Others : %d Total : %d\r",tcp,udp,icmp,igmp,others,total); } void PrintIpHeader (unsigned char* Buffer, int Size) { unsigned short iphdrlen; iphdr = (IPV4_HDR *)Buffer; iphdrlen = iphdr->ip_header_len*4; memset(&source, 0, sizeof(source)); source.sin_addr.s_addr = iphdr->ip_srcaddr; memset(&dest, 0, sizeof(dest)); dest.sin_addr.s_addr = iphdr->ip_destaddr; fprintf(logfile,"\n"); fprintf(logfile,"IP Header\n"); fprintf(logfile," |-IP Version : %d\n",(unsigned int)iphdr->ip_version); fprintf(logfile," |-IP Header Length : %d DWORDS or %d Bytes\n",(unsigned int)iphdr->ip_header_len); fprintf(logfile," |-Type Of Service : %d\n",(unsigned int)iphdr->ip_tos); fprintf(logfile," |-IP Total Length : %d Bytes(Size of Packet)\n",ntohs(iphdr->ip_total_length)); fprintf(logfile," |-Identification : %d\n",ntohs(iphdr->ip_id)); fprintf(logfile," |-Reserved ZERO Field : %d\n",(unsigned int)iphdr->ip_reserved_zero); fprintf(logfile," |-Dont Fragment Field : %d\n",(unsigned int)iphdr->ip_dont_fragment); fprintf(logfile," |-More Fragment Field : %d\n",(unsigned int)iphdr->ip_more_fragment); fprintf(logfile," |-TTL : %d\n",(unsigned int)iphdr->ip_ttl); fprintf(logfile," |-Protocol : %d\n",(unsigned int)iphdr->ip_protocol); fprintf(logfile," |-Checksum : %d\n",ntohs(iphdr->ip_checksum)); fprintf(logfile," |-Source IP : %s\n",inet_ntoa(source.sin_addr)); fprintf(logfile," |-Destination IP : %s\n",inet_ntoa(dest.sin_addr)); } void PrintUdpPacket(unsigned char *Buffer,int Size) { unsigned short iphdrlen; iphdr = (IPV4_HDR *)Buffer; iphdrlen = iphdr->ip_header_len*4; udpheader = (UDP_HDR *)(Buffer + iphdrlen); fprintf(logfile,"\n\n***********************UDP Packet*************************\n"); PrintIpHeader(Buffer,Size); fprintf(logfile,"\nUDP Header\n"); fprintf(logfile," |-Source Port : %d\n",ntohs(udpheader->source_port)); fprintf(logfile," |-Destination Port : %d\n",ntohs(udpheader->dest_port)); fprintf(logfile," |-UDP Length : %d\n",ntohs(udpheader->udp_length)); fprintf(logfile," |-UDP Checksum : %d\n",ntohs(udpheader->udp_checksum)); fprintf(logfile,"\n"); fprintf(logfile,"IP Header\n"); PrintData(Buffer,iphdrlen); fprintf(logfile,"UDP Header\n"); PrintData(Buffer+iphdrlen,sizeof(UDP_HDR)); fprintf(logfile,"Data Payload\n"); PrintData(Buffer+iphdrlen+sizeof(UDP_HDR) ,(Size - sizeof(UDP_HDR) - iphdr->ip_header_len*4)); fprintf(logfile,"\n###########################################################"); } void PrintData (unsigned char* data , int Size) { for(i=0 ; i < Size ; i++) { if( i!=0 && i%16==0) //if one line of hex printing is complete... { fprintf(logfile," "); for(j=i-16 ; j<i ; j++) { if(data[j]>=32 && data[j]<=128) fprintf(logfile,"%c",(unsigned char)data[j]); //if its a number or alphabet else fprintf(logfile,"."); //otherwise print a dot } fprintf(logfile,"\n"); } if(i%16==0) fprintf(logfile," "); fprintf(logfile," %02X",(unsigned int)data[i]); if( i==Size-1) //print the last spaces { for(j=0;j<15-i%16;j++) fprintf(logfile," "); //extra spaces fprintf(logfile," "); for(j=i-i%16 ; j<=i ; j++) { if(data[j]>=32 && data[j]<=128) fprintf(logfile,"%c",(unsigned char)data[j]); else fprintf(logfile,"."); } fprintf(logfile,"\n"); } } } following are the errors Error 1 error LNK2019: unresolved external symbol __imp__WSACleanup@0 referenced in function _main sniffer.obj sniffer test Error 2 error LNK2019: unresolved external symbol __imp__closesocket@4 referenced in function _main sniffer.obj sniffer test Error 3 error LNK2019: unresolved external symbol __imp__WSAIoctl@36 referenced in function _main sniffer.obj sniffer test Error 4 error LNK2019: unresolved external symbol __imp__bind@12 referenced in function _main sniffer.obj sniffer test Error 5 error LNK2019: unresolved external symbol __imp__inet_ntoa@4 referenced in function _main sniffer.obj sniffer test Error 6 error LNK2019: unresolved external symbol __imp__gethostbyname@4 referenced in function _main sniffer.obj sniffer test Error 7 error LNK2019: unresolved external symbol __imp__WSAGetLastError@0 referenced in function _main sniffer.obj sniffer test Error 8 error LNK2019: unresolved external symbol __imp__gethostname@8 referenced in function _main sniffer.obj sniffer test Error 9 error LNK2019: unresolved external symbol __imp__socket@12 referenced in function _main sniffer.obj sniffer test Error 10 error LNK2019: unresolved external symbol __imp__WSAStartup@8 referenced in function _main sniffer.obj sniffer test Error 11 error LNK2019: unresolved external symbol __imp__recvfrom@24 referenced in function "void __cdecl StartSniffing(unsigned int)" (?StartSniffing@@YAXI@Z) sniffer.obj sniffer test Error 12 error LNK2019: unresolved external symbol __imp__ntohs@4 referenced in function "void __cdecl PrintIpHeader(unsigned char *,int)" (?PrintIpHeader@@YAXPAEH@Z) sniffer.obj sniffer test Error 13 fatal error LNK1120: 12 unresolved externals E:\CWM\sniffer test\Debug\sniffer test.exe sniffer test

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  • Could not load type 'Default.DataMatch' in DataMatch.aspx file

    - by salvationishere
    I am developing a C# VS 2008 / SQL Server 2008 website, but now I am getting the above error when I build it. I included the Default.aspx, Default.aspx.cs, DataMatch.aspx, and DataMatch.aspx.cs files below. What do I need to do to fix this? Default.aspx: <%@ Page Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" Title="Untitled Page" %> ... DataMatch.aspx: <%@ Page Language="C#" AutoEventWireup="true" CodeBehind="DataMatch.aspx.cs" Inherits="_Default.DataMatch" %> ... Default.aspx.cs: using System; using System.Collections; using System.Configuration; using System.Data; using System.Linq; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.HtmlControls; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Xml.Linq; using System.Collections.Generic; using System.IO; using System.Drawing; using System.ComponentModel; using System.Data.SqlClient; using ADONET_namespace; using System.Security.Principal; //using System.Windows; public partial class _Default : System.Web.UI.Page //namespace AddFileToSQL { //protected System.Web.UI.HtmlControls.HtmlInputFile uploadFile; //protected System.Web.UI.HtmlControls.HtmlInputButton btnOWrite; //protected System.Web.UI.HtmlControls.HtmlInputButton btnAppend; protected System.Web.UI.WebControls.Label Label1; protected static string inputfile = ""; public static string targettable; public static string selection; // Number of controls added to view state protected int default_NumberOfControls { get { if (ViewState["default_NumberOfControls"] != null) { return (int)ViewState["default_NumberOfControls"]; } else { return 0; } } set { ViewState["default_NumberOfControls"] = value; } } protected void uploadFile_onclick(object sender, EventArgs e) { } protected void Load_GridData() { //GridView1.DataSource = ADONET_methods.DisplaySchemaTables(); //GridView1.DataBind(); } protected void btnOWrite_Click(object sender, EventArgs e) { if (uploadFile.PostedFile.ContentLength > 0) { feedbackLabel.Text = "You do not have sufficient access to overwrite table records."; } else { feedbackLabel.Text = "This file does not contain any data."; } } protected void btnAppend_Click(object sender, EventArgs e) { string fullpath = Page.Request.PhysicalApplicationPath; string path = uploadFile.PostedFile.FileName; if (File.Exists(path)) { // Create a file to write to. try { StreamReader sr = new StreamReader(path); string s = ""; while (sr.Peek() > 0) s = sr.ReadLine(); sr.Close(); } catch (IOException exc) { Console.WriteLine(exc.Message + "Cannot open file."); return; } } if (uploadFile.PostedFile.ContentLength > 0) { inputfile = System.IO.File.ReadAllText(path); Session["Message"] = inputfile; Response.Redirect("DataMatch.aspx"); } else { feedbackLabel.Text = "This file does not contain any data."; } } protected void Page_Load(object sender, EventArgs e) { if (Request.IsAuthenticated) { WelcomeBackMessage.Text = "Welcome back, " + User.Identity.Name + "!"; // Reference the CustomPrincipal / CustomIdentity CustomIdentity ident = User.Identity as CustomIdentity; if (ident != null) WelcomeBackMessage.Text += string.Format(" You are the {0} of {1}.", ident.Title, ident.CompanyName); AuthenticatedMessagePanel.Visible = true; AnonymousMessagePanel.Visible = false; if (!Page.IsPostBack) { Load_GridData(); } } else { AuthenticatedMessagePanel.Visible = false; AnonymousMessagePanel.Visible = true; } } protected void GridView1_SelectedIndexChanged(object sender, EventArgs e) { GridViewRow row = GridView1.SelectedRow; targettable = row.Cells[2].Text; } } DataMatch.aspx.cs: using System; using System.Collections; using System.Collections.Generic; using System.Data; using System.Data.SqlClient; using System.Diagnostics; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; using ADONET_namespace; //using MatrixApp; //namespace AddFileToSQL //{ public partial class DataMatch : AddFileToSQL._Default { protected System.Web.UI.WebControls.PlaceHolder phTextBoxes; protected System.Web.UI.WebControls.PlaceHolder phDropDownLists; protected System.Web.UI.WebControls.Button btnAnotherRequest; protected System.Web.UI.WebControls.Panel pnlCreateData; protected System.Web.UI.WebControls.Literal lTextData; protected System.Web.UI.WebControls.Panel pnlDisplayData; protected static string inputfile2; static string[] headers = null; static string[] data = null; static string[] data2 = null; static DataTable myInputFile = new DataTable("MyInputFile"); static string[] myUserSelections; static bool restart = false; private DropDownList[] newcol; int @temp = 0; string @tempS = ""; string @tempT = ""; // a Property that manages a counter stored in ViewState protected int NumberOfControls { get { return (int)ViewState["NumControls"]; } set { ViewState["NumControls"] = value; } } private Hashtable ddl_ht { get { return (Hashtable)ViewState["ddl_ht"]; } set { ViewState["ddl_ht"] = value; } } // Page Load private void Page_Load(object sender, System.EventArgs e) { if (!Page.IsPostBack) { ddl_ht = new Hashtable(); this.NumberOfControls = 0; } } // This data comes from input file private void PopulateFileInputTable() { myInputFile.Columns.Clear(); string strInput, newrow; string[] oneRow; DataColumn myDataColumn; DataRow myDataRow; int result, numRows; //Read the input file strInput = Session["Message"].ToString(); data = strInput.Split('\r'); //Headers headers = data[0].Split('|'); //Data for (int i = 0; i < data.Length; i++) { newrow = data[i].TrimStart('\n'); data[i] = newrow; } result = String.Compare(data[data.Length - 1], ""); numRows = data.Length; if (result == 0) { numRows = numRows - 1; } data2 = new string[numRows]; for (int a = 0, b = 0; a < numRows; a++, b++) { data2[b] = data[a]; } // Create columns for (int col = 0; col < headers.Length; col++) { @temp = (col + 1); @tempS = @temp.ToString(); @tempT = "@col"+ @temp.ToString(); myDataColumn = new DataColumn(); myDataColumn.DataType = Type.GetType("System.String"); myDataColumn.ColumnName = headers[col]; myInputFile.Columns.Add(myDataColumn); ddl_ht.Add(@tempT, headers[col]); } // Create new DataRow objects and add to DataTable. for (int r = 0; r < numRows - 1; r++) { oneRow = data2[r + 1].Split('|'); myDataRow = myInputFile.NewRow(); for (int c = 0; c < headers.Length; c++) { myDataRow[c] = oneRow[c]; } myInputFile.Rows.Add(myDataRow); } NumberOfControls = headers.Length; myUserSelections = new string[NumberOfControls]; } //Create display panel private void CreateDisplayPanel() { btnSubmit.Style.Add("top", "auto"); btnSubmit.Style.Add("left", "auto"); btnSubmit.Style.Add("position", "absolute"); btnSubmit.Style.Add("top", "200px"); btnSubmit.Style.Add("left", "400px"); newcol = CreateDropDownLists(); for (int counter = 0; counter < NumberOfControls; counter++) { pnlDisplayData.Controls.Add(newcol[counter]); pnlDisplayData.Controls.Add(new LiteralControl("<br><br><br>")); pnlDisplayData.Visible = true; pnlDisplayData.FindControl(newcol[counter].ID); } } //Recreate display panel private void RecreateDisplayPanel() { btnSubmit.Style.Add("top", "auto"); btnSubmit.Style.Add("left", "auto"); btnSubmit.Style.Add("position", "absolute"); btnSubmit.Style.Add("top", "200px"); btnSubmit.Style.Add("left", "400px"); newcol = RecreateDropDownLists(); for (int counter = 0; counter < NumberOfControls; counter++) { pnlDisplayData.Controls.Add(newcol[counter]); pnlDisplayData.Controls.Add(new LiteralControl("<br><br><br>")); pnlDisplayData.Visible = true; pnlDisplayData.FindControl(newcol[counter].ID); } } // Add DropDownList Control to Placeholder private DropDownList[] CreateDropDownLists() { DropDownList[] dropDowns = new DropDownList[NumberOfControls]; for (int counter = 0; counter < NumberOfControls; counter++) { DropDownList ddl = new DropDownList(); SqlDataReader dr2 = ADONET_methods.DisplayTableColumns(targettable); ddl.ID = "DropDownListID" + counter.ToString(); int NumControls = targettable.Length; DataTable dt = new DataTable(); dt.Load(dr2); ddl.DataValueField = "COLUMN_NAME"; ddl.DataTextField = "COLUMN_NAME"; ddl.DataSource = dt; ddl.SelectedIndexChanged += new EventHandler(ddlList_SelectedIndexChanged); ddl.DataBind(); ddl.AutoPostBack = true; ddl.EnableViewState = true; //Preserves View State info on Postbacks dr2.Close(); ddl.Items.Add("IGNORE"); dropDowns[counter] = ddl; } return dropDowns; } protected void ddlList_SelectedIndexChanged(object sender, EventArgs e) { DropDownList ddl = (DropDownList)sender; string ID = ddl.ID; } // Add TextBoxes Control to Placeholder private DropDownList[] RecreateDropDownLists() { DropDownList[] dropDowns = new DropDownList[NumberOfControls]; for (int counter = 0; counter < NumberOfControls; counter++) { DropDownList ddl = new DropDownList(); SqlDataReader dr2 = ADONET_methods.DisplayTableColumns(targettable); ddl.ID = "DropDownListID" + counter.ToString(); int NumControls = targettable.Length; DataTable dt = new DataTable(); dt.Load(dr2); ddl.DataValueField = "COLUMN_NAME"; ddl.DataTextField = "COLUMN_NAME"; ddl.DataSource = dt; ddl.SelectedIndexChanged += new EventHandler(ddlList_SelectedIndexChanged); ddl.DataBind(); ddl.AutoPostBack = true; ddl.EnableViewState = false; //Preserves View State info on Postbacks dr2.Close(); ddl.Items.Add("IGNORE"); dropDowns[counter] = ddl; } return dropDowns; } private void CreateLabels() { for (int counter = 0; counter < NumberOfControls; counter++) { Label lbl = new Label(); lbl.ID = "Label" + counter.ToString(); lbl.Text = headers[counter]; lbl.Style["position"] = "absolute"; lbl.Style["top"] = 60 * counter + 10 + "px"; lbl.Style["left"] = 250 + "px"; pnlDisplayData.Controls.Add(lbl); pnlDisplayData.Controls.Add(new LiteralControl("<br><br><br>")); } } // Add TextBoxes Control to Placeholder private void RecreateLabels() { for (int counter = 0; counter < NumberOfControls; counter++) { Label lbl = new Label(); lbl.ID = "Label" + counter.ToString(); lbl.Text = headers[counter]; lbl.Style["position"] = "absolute"; lbl.Style["top"] = 60 * counter + 10 + "px"; lbl.Style["left"] = 250 + "px"; pnlDisplayData.Controls.Add(lbl); pnlDisplayData.Controls.Add(new LiteralControl("<br><br><br>")); } } // Create TextBoxes and DropDownList data here on postback. protected override void CreateChildControls() { // create the child controls if the server control does not contains child controls this.EnsureChildControls(); // Creates a new ControlCollection. this.CreateControlCollection(); // Here we are recreating controls to persist the ViewState on every post back if (Page.IsPostBack) { RecreateDisplayPanel(); RecreateLabels(); } // Create these conrols when asp.net page is created else { PopulateFileInputTable(); CreateDisplayPanel(); CreateLabels(); } // Prevent dropdownlists and labels from being created again. if (restart == false) { this.ChildControlsCreated = true; } else if (restart == true) { this.ChildControlsCreated = false; } } private void AppendRecords() { switch (targettable) { case "ContactType": for (int r = 0; r < myInputFile.Rows.Count; r++) { resultLabel.Text = ADONET_methods.AppendDataCT(myInputFile.Rows[r], ddl_ht); } break; case "Contact": for (int r = 0; r < myInputFile.Rows.Count; r++) { resultLabel.Text = ADONET_methods.AppendDataC(myInputFile.Rows[r], ddl_ht); } break; case "AddressType": for (int r = 0; r < myInputFile.Rows.Count; r++) { resultLabel.Text = ADONET_methods.AppendDataAT(myInputFile.Rows[r], ddl_ht); } break; default: resultLabel.Text = "You do not have access to modify this table. Please select a different target table and try again."; restart = true; break; //throw new ArgumentOutOfRangeException("targettable type", targettable); } } // Read all the data from TextBoxes and DropDownLists protected void btnSubmit_Click(object sender, System.EventArgs e) { //int cnt = FindOccurence("DropDownListID"); AppendRecords(); pnlDisplayData.Visible = false; btnSubmit.Visible = false; resultLabel.Attributes.Add("style", "align:center"); btnSubmit.Style.Add("top", "auto"); btnSubmit.Style.Add("left", "auto"); btnSubmit.Style.Add("position", "absolute"); int bSubmitPosition = NumberOfControls; btnSubmit.Style.Add("top", System.Convert.ToString(bSubmitPosition)+"px"); resultLabel.Visible = true; Instructions.Visible = false; if (restart == true) { CreateChildControls(); } } private int FindOccurence(string substr) { string reqstr = Request.Form.ToString(); return ((reqstr.Length - reqstr.Replace(substr, "").Length) / substr.Length); } #region Web Form Designer generated code override protected void OnInit(EventArgs e) { // // CODEGEN: This call is required by the ASP.NET Web Form Designer. // InitializeComponent(); base.OnInit(e); } /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { } #endregion } //}

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  • Dynamic Type to do away with Reflection

    - by Rick Strahl
    The dynamic type in C# 4.0 is a welcome addition to the language. One thing I’ve been doing a lot with it is to remove explicit Reflection code that’s often necessary when you ‘dynamically’ need to walk and object hierarchy. In the past I’ve had a number of ReflectionUtils that used string based expressions to walk an object hierarchy. With the introduction of dynamic much of the ReflectionUtils code can be removed for cleaner code that runs considerably faster to boot. The old Way - Reflection Here’s a really contrived example, but assume for a second, you’d want to dynamically retrieve a Page.Request.Url.AbsoluteUrl based on a Page instance in an ASP.NET Web Page request. The strongly typed version looks like this: string path = Page.Request.Url.AbsolutePath; Now assume for a second that Page wasn’t available as a strongly typed instance and all you had was an object reference to start with and you couldn’t cast it (right I said this was contrived :-)) If you’re using raw Reflection code to retrieve this you’d end up writing 3 sets of Reflection calls using GetValue(). Here’s some internal code I use to retrieve Property values as part of ReflectionUtils: /// <summary> /// Retrieve a property value from an object dynamically. This is a simple version /// that uses Reflection calls directly. It doesn't support indexers. /// </summary> /// <param name="instance">Object to make the call on</param> /// <param name="property">Property to retrieve</param> /// <returns>Object - cast to proper type</returns> public static object GetProperty(object instance, string property) { return instance.GetType().GetProperty(property, ReflectionUtils.MemberAccess).GetValue(instance, null); } If you want more control over properties and support both fields and properties as well as array indexers a little more work is required: /// <summary> /// Parses Properties and Fields including Array and Collection references. /// Used internally for the 'Ex' Reflection methods. /// </summary> /// <param name="Parent"></param> /// <param name="Property"></param> /// <returns></returns> private static object GetPropertyInternal(object Parent, string Property) { if (Property == "this" || Property == "me") return Parent; object result = null; string pureProperty = Property; string indexes = null; bool isArrayOrCollection = false; // Deal with Array Property if (Property.IndexOf("[") > -1) { pureProperty = Property.Substring(0, Property.IndexOf("[")); indexes = Property.Substring(Property.IndexOf("[")); isArrayOrCollection = true; } // Get the member MemberInfo member = Parent.GetType().GetMember(pureProperty, ReflectionUtils.MemberAccess)[0]; if (member.MemberType == MemberTypes.Property) result = ((PropertyInfo)member).GetValue(Parent, null); else result = ((FieldInfo)member).GetValue(Parent); if (isArrayOrCollection) { indexes = indexes.Replace("[", string.Empty).Replace("]", string.Empty); if (result is Array) { int Index = -1; int.TryParse(indexes, out Index); result = CallMethod(result, "GetValue", Index); } else if (result is ICollection) { if (indexes.StartsWith("\"")) { // String Index indexes = indexes.Trim('\"'); result = CallMethod(result, "get_Item", indexes); } else { // assume numeric index int index = -1; int.TryParse(indexes, out index); result = CallMethod(result, "get_Item", index); } } } return result; } /// <summary> /// Returns a property or field value using a base object and sub members including . syntax. /// For example, you can access: oCustomer.oData.Company with (this,"oCustomer.oData.Company") /// This method also supports indexers in the Property value such as: /// Customer.DataSet.Tables["Customers"].Rows[0] /// </summary> /// <param name="Parent">Parent object to 'start' parsing from. Typically this will be the Page.</param> /// <param name="Property">The property to retrieve. Example: 'Customer.Entity.Company'</param> /// <returns></returns> public static object GetPropertyEx(object Parent, string Property) { Type type = Parent.GetType(); int at = Property.IndexOf("."); if (at < 0) { // Complex parse of the property return GetPropertyInternal(Parent, Property); } // Walk the . syntax - split into current object (Main) and further parsed objects (Subs) string main = Property.Substring(0, at); string subs = Property.Substring(at + 1); // Retrieve the next . section of the property object sub = GetPropertyInternal(Parent, main); // Now go parse the left over sections return GetPropertyEx(sub, subs); } As you can see there’s a fair bit of code involved into retrieving a property or field value reliably especially if you want to support array indexer syntax. This method is then used by a variety of routines to retrieve individual properties including one called GetPropertyEx() which can walk the dot syntax hierarchy easily. Anyway with ReflectionUtils I can  retrieve Page.Request.Url.AbsolutePath using code like this: string url = ReflectionUtils.GetPropertyEx(Page, "Request.Url.AbsolutePath") as string; This works fine, but is bulky to write and of course requires that I use my custom routines. It’s also quite slow as the code in GetPropertyEx does all sorts of string parsing to figure out which members to walk in the hierarchy. Enter dynamic – way easier! .NET 4.0’s dynamic type makes the above really easy. The following code is all that it takes: object objPage = Page; // force to object for contrivance :) dynamic page = objPage; // convert to dynamic from untyped object string scriptUrl = page.Request.Url.AbsolutePath; The dynamic type assignment in the first two lines turns the strongly typed Page object into a dynamic. The first assignment is just part of the contrived example to force the strongly typed Page reference into an untyped value to demonstrate the dynamic member access. The next line then just creates the dynamic type from the Page reference which allows you to access any public properties and methods easily. It also lets you access any child properties as dynamic types so when you look at Intellisense you’ll see something like this when typing Request.: In other words any dynamic value access on an object returns another dynamic object which is what allows the walking of the hierarchy chain. Note also that the result value doesn’t have to be explicitly cast as string in the code above – the compiler is perfectly happy without the cast in this case inferring the target type based on the type being assigned to. The dynamic conversion automatically handles the cast when making the final assignment which is nice making for natural syntnax that looks *exactly* like the fully typed syntax, but is completely dynamic. Note that you can also use indexers in the same natural syntax so the following also works on the dynamic page instance: string scriptUrl = page.Request.ServerVariables["SCRIPT_NAME"]; The dynamic type is going to make a lot of Reflection code go away as it’s simply so much nicer to be able to use natural syntax to write out code that previously required nasty Reflection syntax. Another interesting thing about the dynamic type is that it actually works considerably faster than Reflection. Check out the following methods that check performance: void Reflection() { Stopwatch stop = new Stopwatch(); stop.Start(); for (int i = 0; i < reps; i++) { // string url = ReflectionUtils.GetProperty(Page,"Title") as string;// "Request.Url.AbsolutePath") as string; string url = Page.GetType().GetProperty("Title", ReflectionUtils.MemberAccess).GetValue(Page, null) as string; } stop.Stop(); Response.Write("Reflection: " + stop.ElapsedMilliseconds.ToString()); } void Dynamic() { Stopwatch stop = new Stopwatch(); stop.Start(); dynamic page = Page; for (int i = 0; i < reps; i++) { string url = page.Title; //Request.Url.AbsolutePath; } stop.Stop(); Response.Write("Dynamic: " + stop.ElapsedMilliseconds.ToString()); } The dynamic code runs in 4-5 milliseconds while the Reflection code runs around 200+ milliseconds! There’s a bit of overhead in the first dynamic object call but subsequent calls are blazing fast and performance is actually much better than manual Reflection. Dynamic is definitely a huge win-win situation when you need dynamic access to objects at runtime.© Rick Strahl, West Wind Technologies, 2005-2010Posted in .NET  CSharp  

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  • Using LINQ Distinct: With an Example on ASP.NET MVC SelectListItem

    - by Joe Mayo
    One of the things that might be surprising in the LINQ Distinct standard query operator is that it doesn’t automatically work properly on custom classes. There are reasons for this, which I’ll explain shortly. The example I’ll use in this post focuses on pulling a unique list of names to load into a drop-down list. I’ll explain the sample application, show you typical first shot at Distinct, explain why it won’t work as you expect, and then demonstrate a solution to make Distinct work with any custom class. The technologies I’m using are  LINQ to Twitter, LINQ to Objects, Telerik Extensions for ASP.NET MVC, ASP.NET MVC 2, and Visual Studio 2010. The function of the example program is to show a list of people that I follow.  In Twitter API vernacular, these people are called “Friends”; though I’ve never met most of them in real life. This is part of the ubiquitous language of social networking, and Twitter in particular, so you’ll see my objects named accordingly. Where Distinct comes into play is because I want to have a drop-down list with the names of the friends appearing in the list. Some friends are quite verbose, which means I can’t just extract names from each tweet and populate the drop-down; otherwise, I would end up with many duplicate names. Therefore, Distinct is the appropriate operator to eliminate the extra entries from my friends who tend to be enthusiastic tweeters. The sample doesn’t do anything with the drop-down list and I leave that up to imagination for what it’s practical purpose could be; perhaps a filter for the list if I only want to see a certain person’s tweets or maybe a quick list that I plan to combine with a TextBox and Button to reply to a friend. When the program runs, you’ll need to authenticate with Twitter, because I’m using OAuth (DotNetOpenAuth), for authentication, and then you’ll see the drop-down list of names above the grid with the most recent tweets from friends. Here’s what the application looks like when it runs: As you can see, there is a drop-down list above the grid. The drop-down list is where most of the focus of this article will be. There is some description of the code before we talk about the Distinct operator, but we’ll get there soon. This is an ASP.NET MVC2 application, written with VS 2010. Here’s the View that produces this screen: <%@ Page Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<TwitterFriendsViewModel>" %> <%@ Import Namespace="DistinctSelectList.Models" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server">     Home Page </asp:Content><asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server">     <fieldset>         <legend>Twitter Friends</legend>         <div>             <%= Html.DropDownListFor(                     twendVM => twendVM.FriendNames,                     Model.FriendNames,                     "<All Friends>") %>         </div>         <div>             <% Html.Telerik().Grid<TweetViewModel>(Model.Tweets)                    .Name("TwitterFriendsGrid")                    .Columns(cols =>                     {                         cols.Template(col =>                             { %>                                 <img src="<%= col.ImageUrl %>"                                      alt="<%= col.ScreenName %>" />                         <% });                         cols.Bound(col => col.ScreenName);                         cols.Bound(col => col.Tweet);                     })                    .Render(); %>         </div>     </fieldset> </asp:Content> As shown above, the Grid is from Telerik’s Extensions for ASP.NET MVC. The first column is a template that renders the user’s Avatar from a URL provided by the Twitter query. Both the Grid and DropDownListFor display properties that are collections from a TwitterFriendsViewModel class, shown below: using System.Collections.Generic; using System.Web.Mvc; namespace DistinctSelectList.Models { /// /// For finding friend info on screen /// public class TwitterFriendsViewModel { /// /// Display names of friends in drop-down list /// public List FriendNames { get; set; } /// /// Display tweets in grid /// public List Tweets { get; set; } } } I created the TwitterFreindsViewModel. The two Lists are what the View consumes to populate the DropDownListFor and Grid. Notice that FriendNames is a List of SelectListItem, which is an MVC class. Another custom class I created is the TweetViewModel (the type of the Tweets List), shown below: namespace DistinctSelectList.Models { /// /// Info on friend tweets /// public class TweetViewModel { /// /// User's avatar /// public string ImageUrl { get; set; } /// /// User's Twitter name /// public string ScreenName { get; set; } /// /// Text containing user's tweet /// public string Tweet { get; set; } } } The initial Twitter query returns much more information than we need for our purposes and this a special class for displaying info in the View.  Now you know about the View and how it’s constructed. Let’s look at the controller next. The controller for this demo performs authentication, data retrieval, data manipulation, and view selection. I’ll skip the description of the authentication because it’s a normal part of using OAuth with LINQ to Twitter. Instead, we’ll drill down and focus on the Distinct operator. However, I’ll show you the entire controller, below,  so that you can see how it all fits together: using System.Linq; using System.Web.Mvc; using DistinctSelectList.Models; using LinqToTwitter; namespace DistinctSelectList.Controllers { [HandleError] public class HomeController : Controller { private MvcOAuthAuthorization auth; private TwitterContext twitterCtx; /// /// Display a list of friends current tweets /// /// public ActionResult Index() { auth = new MvcOAuthAuthorization(InMemoryTokenManager.Instance, InMemoryTokenManager.AccessToken); string accessToken = auth.CompleteAuthorize(); if (accessToken != null) { InMemoryTokenManager.AccessToken = accessToken; } if (auth.CachedCredentialsAvailable) { auth.SignOn(); } else { return auth.BeginAuthorize(); } twitterCtx = new TwitterContext(auth); var friendTweets = (from tweet in twitterCtx.Status where tweet.Type == StatusType.Friends select new TweetViewModel { ImageUrl = tweet.User.ProfileImageUrl, ScreenName = tweet.User.Identifier.ScreenName, Tweet = tweet.Text }) .ToList(); var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct() .ToList(); var twendsVM = new TwitterFriendsViewModel { Tweets = friendTweets, FriendNames = friendNames }; return View(twendsVM); } public ActionResult About() { return View(); } } } The important part of the listing above are the LINQ to Twitter queries for friendTweets and friendNames. Both of these results are used in the subsequent population of the twendsVM instance that is passed to the view. Let’s dissect these two statements for clarification and focus on what is happening with Distinct. The query for friendTweets gets a list of the 20 most recent tweets (as specified by the Twitter API for friend queries) and performs a projection into the custom TweetViewModel class, repeated below for your convenience: var friendTweets = (from tweet in twitterCtx.Status where tweet.Type == StatusType.Friends select new TweetViewModel { ImageUrl = tweet.User.ProfileImageUrl, ScreenName = tweet.User.Identifier.ScreenName, Tweet = tweet.Text }) .ToList(); The LINQ to Twitter query above simplifies what we need to work with in the View and the reduces the amount of information we have to look at in subsequent queries. Given the friendTweets above, the next query performs another projection into an MVC SelectListItem, which is required for binding to the DropDownList.  This brings us to the focus of this blog post, writing a correct query that uses the Distinct operator. The query below uses LINQ to Objects, querying the friendTweets collection to get friendNames: var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct() .ToList(); The above implementation of Distinct seems normal, but it is deceptively incorrect. After running the query above, by executing the application, you’ll notice that the drop-down list contains many duplicates.  This will send you back to the code scratching your head, but there’s a reason why this happens. To understand the problem, we must examine how Distinct works in LINQ to Objects. Distinct has two overloads: one without parameters, as shown above, and another that takes a parameter of type IEqualityComparer<T>.  In the case above, no parameters, Distinct will call EqualityComparer<T>.Default behind the scenes to make comparisons as it iterates through the list. You don’t have problems with the built-in types, such as string, int, DateTime, etc, because they all implement IEquatable<T>. However, many .NET Framework classes, such as SelectListItem, don’t implement IEquatable<T>. So, what happens is that EqualityComparer<T>.Default results in a call to Object.Equals, which performs reference equality on reference type objects.  You don’t have this problem with value types because the default implementation of Object.Equals is bitwise equality. However, most of your projections that use Distinct are on classes, just like the SelectListItem used in this demo application. So, the reason why Distinct didn’t produce the results we wanted was because we used a type that doesn’t define its own equality and Distinct used the default reference equality. This resulted in all objects being included in the results because they are all separate instances in memory with unique references. As you might have guessed, the solution to the problem is to use the second overload of Distinct that accepts an IEqualityComparer<T> instance. If you were projecting into your own custom type, you could make that type implement IEqualityComparer<T>, but SelectListItem belongs to the .NET Framework Class Library.  Therefore, the solution is to create a custom type to implement IEqualityComparer<T>, as in the SelectListItemComparer class, shown below: using System.Collections.Generic; using System.Web.Mvc; namespace DistinctSelectList.Models { public class SelectListItemComparer : EqualityComparer { public override bool Equals(SelectListItem x, SelectListItem y) { return x.Value.Equals(y.Value); } public override int GetHashCode(SelectListItem obj) { return obj.Value.GetHashCode(); } } } The SelectListItemComparer class above doesn’t implement IEqualityComparer<SelectListItem>, but rather derives from EqualityComparer<SelectListItem>. Microsoft recommends this approach for consistency with the behavior of generic collection classes. However, if your custom type already derives from a base class, go ahead and implement IEqualityComparer<T>, which will still work. EqualityComparer is an abstract class, that implements IEqualityComparer<T> with Equals and GetHashCode abstract methods. For the purposes of this application, the SelectListItem.Value property is sufficient to determine if two items are equal.   Since SelectListItem.Value is type string, the code delegates equality to the string class. The code also delegates the GetHashCode operation to the string class.You might have other criteria in your own object and would need to define what it means for your object to be equal. Now that we have an IEqualityComparer<SelectListItem>, let’s fix the problem. The code below modifies the query where we want distinct values: var friendNames = (from tweet in friendTweets select new SelectListItem { Text = tweet.ScreenName, Value = tweet.ScreenName }) .Distinct(new SelectListItemComparer()) .ToList(); Notice how the code above passes a new instance of SelectListItemComparer as the parameter to the Distinct operator. Now, when you run the application, the drop-down list will behave as you expect, showing only a unique set of names. In addition to Distinct, other LINQ Standard Query Operators have overloads that accept IEqualityComparer<T>’s, You can use the same techniques as shown here, with SelectListItemComparer, with those other operators as well. Now you know how to resolve problems with getting Distinct to work properly and also have a way to fix problems with other operators that require equality comparisons. @JoeMayo

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  • Guarding against CSRF Attacks in ASP.NET MVC2

    - by srkirkland
    Alongside XSS (Cross Site Scripting) and SQL Injection, Cross-site Request Forgery (CSRF) attacks represent the three most common and dangerous vulnerabilities to common web applications today. CSRF attacks are probably the least well known but they are relatively easy to exploit and extremely and increasingly dangerous. For more information on CSRF attacks, see these posts by Phil Haack and Steve Sanderson. The recognized solution for preventing CSRF attacks is to put a user-specific token as a hidden field inside your forms, then check that the right value was submitted. It's best to use a random value which you’ve stored in the visitor’s Session collection or into a Cookie (so an attacker can't guess the value). ASP.NET MVC to the rescue ASP.NET MVC provides an HTMLHelper called AntiForgeryToken(). When you call <%= Html.AntiForgeryToken() %> in a form on your page you will get a hidden input and a Cookie with a random string assigned. Next, on your target Action you need to include [ValidateAntiForgeryToken], which handles the verification that the correct token was supplied. Good, but we can do better Using the AntiForgeryToken is actually quite an elegant solution, but adding [ValidateAntiForgeryToken] on all of your POST methods is not very DRY, and worse can be easily forgotten. Let's see if we can make this easier on the program but moving from an "Opt-In" model of protection to an "Opt-Out" model. Using AntiForgeryToken by default In order to mandate the use of the AntiForgeryToken, we're going to create an ActionFilterAttribute which will do the anti-forgery validation on every POST request. First, we need to create a way to Opt-Out of this behavior, so let's create a quick action filter called BypassAntiForgeryToken: [AttributeUsage(AttributeTargets.Method, AllowMultiple=false)] public class BypassAntiForgeryTokenAttribute : ActionFilterAttribute { } Now we are ready to implement the main action filter which will force anti forgery validation on all post actions within any class it is defined on: [AttributeUsage(AttributeTargets.Class, AllowMultiple = false)] public class UseAntiForgeryTokenOnPostByDefault : ActionFilterAttribute { public override void OnActionExecuting(ActionExecutingContext filterContext) { if (ShouldValidateAntiForgeryTokenManually(filterContext)) { var authorizationContext = new AuthorizationContext(filterContext.Controller.ControllerContext);   //Use the authorization of the anti forgery token, //which can't be inhereted from because it is sealed new ValidateAntiForgeryTokenAttribute().OnAuthorization(authorizationContext); }   base.OnActionExecuting(filterContext); }   /// <summary> /// We should validate the anti forgery token manually if the following criteria are met: /// 1. The http method must be POST /// 2. There is not an existing [ValidateAntiForgeryToken] attribute on the action /// 3. There is no [BypassAntiForgeryToken] attribute on the action /// </summary> private static bool ShouldValidateAntiForgeryTokenManually(ActionExecutingContext filterContext) { var httpMethod = filterContext.HttpContext.Request.HttpMethod;   //1. The http method must be POST if (httpMethod != "POST") return false;   // 2. There is not an existing anti forgery token attribute on the action var antiForgeryAttributes = filterContext.ActionDescriptor.GetCustomAttributes(typeof(ValidateAntiForgeryTokenAttribute), false);   if (antiForgeryAttributes.Length > 0) return false;   // 3. There is no [BypassAntiForgeryToken] attribute on the action var ignoreAntiForgeryAttributes = filterContext.ActionDescriptor.GetCustomAttributes(typeof(BypassAntiForgeryTokenAttribute), false);   if (ignoreAntiForgeryAttributes.Length > 0) return false;   return true; } } The code above is pretty straight forward -- first we check to make sure this is a POST request, then we make sure there aren't any overriding *AntiForgeryTokenAttributes on the action being executed. If we have a candidate then we call the ValidateAntiForgeryTokenAttribute class directly and execute OnAuthorization() on the current authorization context. Now on our base controller, you could use this new attribute to start protecting your site from CSRF vulnerabilities. [UseAntiForgeryTokenOnPostByDefault] public class ApplicationController : System.Web.Mvc.Controller { }   //Then for all of your controllers public class HomeController : ApplicationController {} What we accomplished If your base controller has the new default anti-forgery token attribute on it, when you don't use <%= Html.AntiForgeryToken() %> in a form (or of course when an attacker doesn't supply one), the POST action will throw the descriptive error message "A required anti-forgery token was not supplied or was invalid". Attack foiled! In summary, I think having an anti-CSRF policy by default is an effective way to protect your websites, and it turns out it is pretty easy to accomplish as well. Enjoy!

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  • C#: System.Lazy&lt;T&gt; and the Singleton Design Pattern

    - by James Michael Hare
    So we've all coded a Singleton at one time or another.  It's a really simple pattern and can be a slightly more elegant alternative to global variables.  Make no mistake, Singletons can be abused and are often over-used -- but occasionally you find a Singleton is the most elegant solution. For those of you not familiar with a Singleton, the basic Design Pattern is that a Singleton class is one where there is only ever one instance of the class created.  This means that constructors must be private to avoid users creating their own instances, and a static property (or method in languages without properties) is defined that returns a single static instance. 1: public class Singleton 2: { 3: // the single instance is defined in a static field 4: private static readonly Singleton _instance = new Singleton(); 5:  6: // constructor private so users can't instantiate on their own 7: private Singleton() 8: { 9: } 10:  11: // read-only property that returns the static field 12: public static Singleton Instance 13: { 14: get 15: { 16: return _instance; 17: } 18: } 19: } This is the most basic singleton, notice the key features: Static readonly field that contains the one and only instance. Constructor is private so it can only be called by the class itself. Static property that returns the single instance. Looks like it satisfies, right?  There's just one (potential) problem.  C# gives you no guarantee of when the static field _instance will be created.  This is because the C# standard simply states that classes (which are marked in the IL as BeforeFieldInit) can have their static fields initialized any time before the field is accessed.  This means that they may be initialized on first use, they may be initialized at some other time before, you can't be sure when. So what if you want to guarantee your instance is truly lazy.  That is, that it is only created on first call to Instance?  Well, there's a few ways to do this.  First we'll show the old ways, and then talk about how .Net 4.0's new System.Lazy<T> type can help make the lazy-Singleton cleaner. Obviously, we could take on the lazy construction ourselves, but being that our Singleton may be accessed by many different threads, we'd need to lock it down. 1: public class LazySingleton1 2: { 3: // lock for thread-safety laziness 4: private static readonly object _mutex = new object(); 5:  6: // static field to hold single instance 7: private static LazySingleton1 _instance = null; 8:  9: // property that does some locking and then creates on first call 10: public static LazySingleton1 Instance 11: { 12: get 13: { 14: if (_instance == null) 15: { 16: lock (_mutex) 17: { 18: if (_instance == null) 19: { 20: _instance = new LazySingleton1(); 21: } 22: } 23: } 24:  25: return _instance; 26: } 27: } 28:  29: private LazySingleton1() 30: { 31: } 32: } This is a standard double-check algorithm so that you don't lock if the instance has already been created.  However, because it's possible two threads can go through the first if at the same time the first time back in, you need to check again after the lock is acquired to avoid creating two instances. Pretty straightforward, but ugly as all heck.  Well, you could also take advantage of the C# standard's BeforeFieldInit and define your class with a static constructor.  It need not have a body, just the presence of the static constructor will remove the BeforeFieldInit attribute on the class and guarantee that no fields are initialized until the first static field, property, or method is called.   1: public class LazySingleton2 2: { 3: // because of the static constructor, this won't get created until first use 4: private static readonly LazySingleton2 _instance = new LazySingleton2(); 5:  6: // Returns the singleton instance using lazy-instantiation 7: public static LazySingleton2 Instance 8: { 9: get { return _instance; } 10: } 11:  12: // private to prevent direct instantiation 13: private LazySingleton2() 14: { 15: } 16:  17: // removes BeforeFieldInit on class so static fields not 18: // initialized before they are used 19: static LazySingleton2() 20: { 21: } 22: } Now, while this works perfectly, I hate it.  Why?  Because it's relying on a non-obvious trick of the IL to guarantee laziness.  Just looking at this code, you'd have no idea that it's doing what it's doing.  Worse yet, you may decide that the empty static constructor serves no purpose and delete it (which removes your lazy guarantee).  Worse-worse yet, they may alter the rules around BeforeFieldInit in the future which could change this. So, what do I propose instead?  .Net 4.0 adds the System.Lazy type which guarantees thread-safe lazy-construction.  Using System.Lazy<T>, we get: 1: public class LazySingleton3 2: { 3: // static holder for instance, need to use lambda to construct since constructor private 4: private static readonly Lazy<LazySingleton3> _instance 5: = new Lazy<LazySingleton3>(() => new LazySingleton3()); 6:  7: // private to prevent direct instantiation. 8: private LazySingleton3() 9: { 10: } 11:  12: // accessor for instance 13: public static LazySingleton3 Instance 14: { 15: get 16: { 17: return _instance.Value; 18: } 19: } 20: } Note, you need your lambda to call the private constructor as Lazy's default constructor can only call public constructors of the type passed in (which we can't have by definition of a Singleton).  But, because the lambda is defined inside our type, it has access to the private members so it's perfect. Note how the Lazy<T> makes it obvious what you're doing (lazy construction), instead of relying on an IL generation side-effect.  This way, it's more maintainable.  Lazy<T> has many other uses as well, obviously, but I really love how elegant and readable it makes the lazy Singleton.

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  • Render MVCContrib Grid with No Header Row

    - by Ben Griswold
    The MVCContrib Grid allows for the easy construction of HTML tables for displaying data from a collection of Model objects. I add this component to all of my ASP.NET MVC projects.  If you aren’t familiar with what the grid has to offer, it’s worth the looking into. What you may notice in the busy example below is the fact that I render my column headers independent of the grid contents.  This allows me to keep my headers fixed while the user searches through the table content which is displayed in a scrollable div*.  Thus, I needed a way to render my grid without headers. That’s where Grid Renderers come into play.  <table border="0" cellspacing="0" cellpadding="0" class="projectHeaderTable">     <tr>         <td class="memberTableMemberHeader">             <%= Html.GridColumnHeader("Member", "Index", "MemberFullName")%>              </td>         <td class="memberTableRoleHeader">             <%= Html.GridColumnHeader("Role", "Index", "ProjectRoleTypeName")%>              </td>                <td class="memberTableActionHeader">             Action         </td>     </tr> </table> <div class="scrollContentWrapper"> <% Html.Grid(Model)     .Columns(column =>             {                 column.For(c => c.MemberFullName).Attributes(@class => "memberTableMemberCol");                 column.For(c => c.ProjectRoleTypeName).Attributes(@class => "memberTableRoleCol");                 column.For(x => Html.ActionLink("View", "Details", new { Id = x.ProjectMemberId }) + " | " +                                 Html.ActionLink("Edit", "Edit", new { Id = x.ProjectMemberId }) + " | " +                                 Html.ActionLink("Remove", "Delete", new { Id = x.ProjectMemberId }))                     .Attributes(@class => "memberTableActionCol").DoNotEncode();             })     .Empty("There are no members associated with this project.")     .Attributes(@class => "lbContent")     .RenderUsing(new GridNoHeaderRenderer<ProjectMemberDetailsViewModel>())     .Render(); %> </div> <div class="scrollContentBottom">     <!– –> </div> <%=Html.Pager(Model) %> Maybe you noticed the reference to the GridNoHeaderRenderer class above?  Yep, rendering the grid with no header is straightforward.   public class GridNoHeaderRenderer<T> :     HtmlTableGridRenderer<T> where T: class {     protected override bool RenderHeader()     {         // Explicitly returning true would suppress the header         // just fine, however, Render() will always assume that         // items exist in collection and RenderEmpty() will         // never be called.           // In other words, return ShouldRenderHeader() if you         // want to maintain the Empty text when no items exist.         return ShouldRenderHeader();     } } Well, if you read through the comments, there is one catch.  You might be tempted to have the RenderHeader method always return true.  This would work just fine but you should return the result of ShouldRenderHeader() instead so the Empty text will continue to display if there are no items in the collection. The GridRenderer feature found in the MVCContrib Grid is so well put together, I just had to share.  * Though you can find countless alternatives to the fixed headers problem online, this is the only solution that I’ve ever found to reliably work across browsers. If you know something I don’t, please share.

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  • SmtpClient and Locked File Attachments

    - by Rick Strahl
    Got a note a couple of days ago from a client using one of my generic routines that wraps SmtpClient. Apparently whenever a file has been attached to a message and emailed with SmtpClient the file remains locked after the message has been sent. Oddly this particular issue hasn’t cropped up before for me although these routines are in use in a number of applications I’ve built. The wrapper I use was built mainly to backfit an old pre-.NET 2.0 email client I built using Sockets to avoid the CDO nightmares of the .NET 1.x mail client. The current class retained the same class interface but now internally uses SmtpClient which holds a flat property interface that makes it less verbose to send off email messages. File attachments in this interface are handled by providing a comma delimited list for files in an Attachments string property which is then collected along with the other flat property settings and eventually passed on to SmtpClient in the form of a MailMessage structure. The jist of the code is something like this: /// <summary> /// Fully self contained mail sending method. Sends an email message by connecting /// and disconnecting from the email server. /// </summary> /// <returns>true or false</returns> public bool SendMail() { if (!this.Connect()) return false; try { // Create and configure the message MailMessage msg = this.GetMessage(); smtp.Send(msg); this.OnSendComplete(this); } catch (Exception ex) { string msg = ex.Message; if (ex.InnerException != null) msg = ex.InnerException.Message; this.SetError(msg); this.OnSendError(this); return false; } finally { // close connection and clear out headers // SmtpClient instance nulled out this.Close(); } return true; } /// <summary> /// Configures the message interface /// </summary> /// <param name="msg"></param> protected virtual MailMessage GetMessage() { MailMessage msg = new MailMessage(); msg.Body = this.Message; msg.Subject = this.Subject; msg.From = new MailAddress(this.SenderEmail, this.SenderName); if (!string.IsNullOrEmpty(this.ReplyTo)) msg.ReplyTo = new MailAddress(this.ReplyTo); // Send all the different recipients this.AssignMailAddresses(msg.To, this.Recipient); this.AssignMailAddresses(msg.CC, this.CC); this.AssignMailAddresses(msg.Bcc, this.BCC); if (!string.IsNullOrEmpty(this.Attachments)) { string[] files = this.Attachments.Split(new char[2] { ',', ';' }, StringSplitOptions.RemoveEmptyEntries); foreach (string file in files) { msg.Attachments.Add(new Attachment(file)); } } if (this.ContentType.StartsWith("text/html")) msg.IsBodyHtml = true; else msg.IsBodyHtml = false; msg.BodyEncoding = this.Encoding; … additional code omitted return msg; } Basically this code collects all the property settings of the wrapper object and applies them to the SmtpClient and in GetMessage() to an individual MailMessage properties. Specifically notice that attachment filenames are converted from a comma-delimited string to filenames from which new attachments are created. The code as it’s written however, will cause the problem with file attachments not being released properly. Internally .NET opens up stream handles and reads the files from disk to dump them into the email send stream. The attachments are always sent correctly but the local files are not immediately closed. As you probably guessed the issue is simply that some resources are not automatcially disposed when sending is complete and sure enough the following code change fixes the problem: // Create and configure the message using (MailMessage msg = this.GetMessage()) { smtp.Send(msg); if (this.SendComplete != null) this.OnSendComplete(this); // or use an explicit msg.Dispose() here } The Message object requires an explicit call to Dispose() (or a using() block as I have here) to force the attachment files to get closed. I think this is rather odd behavior for this scenario however. The code I use passes in filenames and my expectation of an API that accepts file names is that it uses the files by opening and streaming them and then closing them when done. Why keep the streams open and require an explicit .Dispose() by the calling code which is bound to lead to unexpected behavior just as my customer ran into? Any API level code should clean up as much as possible and this is clearly not happening here resulting in unexpected behavior. Apparently lots of other folks have run into this before as I found based on a few Twitter comments on this topic. Odd to me too is that SmtpClient() doesn’t implement IDisposable – it’s only the MailMessage (and Attachments) that implement it and require it to clean up for left over resources like open file handles. This means that you couldn’t even use a using() statement around the SmtpClient code to resolve this – instead you’d have to wrap it around the message object which again is rather unexpected. Well, chalk that one up to another small unexpected behavior that wasted a half an hour of my time – hopefully this post will help someone avoid this same half an hour of hunting and searching. Resources: Full code to SmptClientNative (West Wind Web Toolkit Repository) SmtpClient Documentation MSDN © Rick Strahl, West Wind Technologies, 2005-2010Posted in .NET  

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  • When returning from a period of not programming, do you find you've improved?

    - by Jon Purdy
    It seems as though whenever I take an extended break from programming—whether to pursue other interests or simply because I fall out of the habit for a while—I invariably find that when I return to a project and set to coding, I come with an abundance of new ideas, novel approaches, and just plain better code. It may be because I have a lot of other creative interests besides programming, and my mind likes to find correlation and crossover between them, so while I'm doing one thing, in the back of my mind I'm usually also applying it to another. So what's your experience? Do you ever return from a break (whether intentional or not) feeling not only refreshed, but also somehow noticeably improved? Is it actually the norm?

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