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  • return the variable used for using inside the using C#

    - by di3go
    Hello, I am returning the variable I am creating in a using statement inside the using statement (sounds funny): public DataTable foo () { using (DataTable properties = new DataTable()) { // do something return properties; } } Will this Dispose the properties variable?? After doing this am still getting this Warning: Warning 34 CA2000 : Microsoft.Reliability : In method 'test.test', call System.IDisposable.Dispose on object 'properties' before all references to it are out of scope. Any Ideas? Thanks

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  • Does a C# using statement perform try/finally?

    - by Lirik
    Suppose that I have the following code: private void UpdateDB(QuoteDataSet dataSet, Strint tableName) { using(SQLiteConnection conn = new SQLiteConnection(_connectionString)) { conn.Open(); using (SQLiteTransaction transaction = conn.BeginTransaction()) { using (SQLiteCommand cmd = new SQLiteCommand("SELECT * FROM " + tableName, conn)) { using (SQLiteDataAdapter sqliteAdapter = new SQLiteDataAdapter()) { sqliteAdapter.Update(dataSet, tableName); } } transaction.Commit(); } } } The C# documentation states that with a using statement the object within the scope will be disposed and I've seen several places where it's suggested that we don't need to use try/finally clause. I usually surround my connections with a try/finally, and I always close the connection in the finally clause. Given the above code, is it reasonable to assume that the connection will be closed if there is an exception?

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  • include and using namespace in C++

    - by cambr
    for using cout, I need to specify both: #include<iostream> and using namespace std; Where is cout defined? in iostream, correct? So, it is that iostream itself is there in namespace std? What is the meaning of both the statements with respect to using cout? I am confused why we need to include them both.

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  • missing a using directive or an assembly reference

    - by cire1507
    I'm in the process of writing a small asp.net mvc application that is using the northwind.mdf. When building the solution I get this error: Error 1 The type or namespace name 'Order' could not be found (are you missing a using directive or an assembly reference?) Order is a table in the northwind database. any help is most appreciated.

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  • The type or namespace cannot be found (are you missing a using directive or an assembly reference?)

    - by Kumu
    I get the following error when I try to compile my C# program: The type or namespace name 'Login' could not be found (are you missing a using directive or an assembly reference?) using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace FootballLeague { public partial class MainMenu : Form { FootballLeagueDatabase footballLeagueDatabase; Game game; Team team; Login login; //Error here public MainMenu() { InitializeComponent(); changePanel(1); } public MainMenu(FootballLeagueDatabase footballLeagueDatabaseIn) { InitializeComponent(); footballLeagueDatabase = footballLeagueDatabaseIn; } private void Form_Loaded(object sender, EventArgs e) { } private void gameButton_Click(object sender, EventArgs e) { int option = 0; changePanel(option); } private void scoreboardButton_Click(object sender, EventArgs e) { int option = 1; changePanel(option); } private void changePanel(int optionIn) { gamePanel.Hide(); scoreboardPanel.Hide(); string title = "Football League System"; switch (optionIn) { case 0: gamePanel.Show(); this.Text = title + " - Game Menu"; break; case 1: scoreboardPanel.Show(); this.Text = title + " - Display Menu"; break; } } private void logoutButton_Click(object sender, EventArgs e) { login = new Login(); login.Show(); this.Hide(); } Login.cs class: using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; namespace FootballLeagueSystem { public partial class Login : Form { MainMenu menu; public Login() { InitializeComponent(); } private void administratorLoginButton_Click(object sender, EventArgs e) { string username1 = "08247739"; string password1 = "08247739"; if ((userNameTxt.Text.Length) == 0) MessageBox.Show("Please enter your username!"); else if ((passwordTxt.Text.Length) == 0) MessageBox.Show("Please enter your password!"); else if (userNameTxt.Text.Equals("") || passwordTxt.Text.Equals("")) MessageBox.Show("Invalid Username or Password!"); else { if (this.userNameTxt.Text == username1 && this.passwordTxt.Text == password1) MessageBox.Show("Welcome Administrator!", "Administrator Login"); menu = new MainMenu(); menu.Show(); this.Hide(); } } private void managerLoginButton_Click(object sender, EventArgs e) { { string username2 = "1111"; string password2 = "1111"; if ((userNameTxt.Text.Length) == 0) MessageBox.Show("Please enter your username!"); else if ((passwordTxt.Text.Length) == 0) MessageBox.Show("Please enter your password!"); else if (userNameTxt.Text.Equals("") && passwordTxt.Text.Equals("")) MessageBox.Show("Invalid Username or Password!"); else { if (this.userNameTxt.Text == username2 && this.passwordTxt.Text == password2) MessageBox.Show("Welcome Manager!", "Manager Login"); menu = new MainMenu(); menu.Show(); this.Hide(); } } } private void cancelButton_Click(object sender, EventArgs e) { this.Close(); } } } Where is the error? What am I doing wrong?

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  • Automate refactor import/using directives, using ReSharper and Visual Studio 2010

    - by Mendy
    I want to automate the Visual Studio 2010 / Resharper 5 auto inserting import directives to put my internal namespaces into the namespace sphere. Like this: using System; using System.Collections.Generic; using System.Linq; using StructureMap; using MyProject.Core; // <--- Move inside. using MyProject.Core.Common; // <--- Move inside. namespace MyProject.DependencyResolution { using Core; using Core.Common; // <--- My internal namespaces to be here! public class DependencyRegistrar { ........... } }

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  • .Net to Oracle Connectivity using ODBC .NET

    - by SAMIR BHOGAYTA
    You can use the new ODBC .NET Data Provider that works with the ODBC Oracle7.x driver or higher. You need to have MDAC 2.6 or later installed and then download ODBC .NET from the MS Web Site http://msdn.microsoft.com/downloads/default.asp?url=/code/sample.asp?url=/msdn-files/027/001/668/msdncompositedoc.xml&frame=true. MDAC (Microsoft Data Access Component) 2.7 contains core component, including the Microsoft SQL server and Oracle OLE Database provider and ODBC driver. Insta ...You can use the new ODBC .NET Data Provider that works with the ODBC Oracle7.x driver or higher. You need to have MDAC 2.6 or later installed and then download ODBC .NET from the MS Web Site http://msdn.microsoft.com/downloads/default.asp?url=/code/sample.asp?url=/msdn-files/027/001/668/msdncompositedoc.xml&frame=true. MDAC (Microsoft Data Access Component) 2.7 contains core component, including the Microsoft SQL server and Oracle OLE Database provider and ODBC driver. Install ODBC .NET from the MS Web Site http://msdn.microsoft.com/downloads/default.asp?URL=/downloads/sample.asp?url=/msdn-files/027/001/943/msdncompositedoc.xml Create a DSN, using either Microsoft ODBC for Oracle or Oracle supplied Driver if the Oracle client software is loaded. here for eq. TrailDSN. While creating DSN give user name along with passward for eq. scott/tiger. using Microsoft .Data.Odbc; private void Form1_Load(object sender, System.EventArgs e) { try { OdbcConnection myconnection= new OdbcConnection ("DSN=TrialDSN"); OdbcDataAdapter myda = new OdbcDataAdapter ("Select * from EMP", myconnection); DataSet ds= new DataSet (); myda.Fill(ds, "Table"); dataGrid1.DataSource = ds ; } catch(Exception ex) { MessageBox.Show (ex.Message ); } }

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  • C# using namespace directive in nested namespaces

    - by MoSlo
    Right, I've usually used 'using' directives as follows using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace AwesomeLib { //awesome award winning class declarations making use of Linq } i've recently seen examples of such as using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace AwesomeLib { //awesome award winning class declarations making use of Linq namespace DataLibrary { using System.Data; //Data access layers and whatnot } } Granted, i understand that i can put USING inside of my namespace declaration. Such a thing makes sense to me if your namespaces are in the same root (they organized). System; namespace 1 {} namespace 2 { System.data; } But what of nested namespaces? Personally, I would leave all USING declarations at the top where you can find them easily. Instead, it looks like they're being spread all over the source file. Is there benefit to the USING directives being used this way in nested namespaces? Such as memory management or the JIT compiler?

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  • Scala: "using" keyword

    - by Albert Cenkier
    i've defined 'using' keyword as following: def using[A, B <: {def close(): Unit}] (closeable: B) (f: B => A): A = try { f(closeable) } finally { closeable.close() } i can use it like that: using(new PrintWriter("sample.txt")){ out => out.println("hellow world!") } now i'm curious how to define 'using' keyword to take any number of parameters, and be able to access them separately: using(new BufferedReader(new FileReader("in.txt")), new PrintWriter("out.txt")){ (in, out) => out.println(in.readLIne) }

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  • .NET using block and return; keyword

    - by Emre
    When I say this using (Entities db = new Entities()) { return db.TableName.AsQueryable().ToList(); } Do I by-pass the functionality of using block since I return something, and the method exits before exiting the using block, so I think the using block will not serve to its purpose and dispose the resource. Is this correct?

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  • VB.NET: question about "using" block

    - by Craig Johnston
    Consider the code: On Error Goto ErrorHandler Using sr As StreamReader = New StreamReader(OpenFile) str = sr.ReadToEnd sr.Close() End Using Exit Sub ErrorHandler: If there is an error inside the Using block how do you clean up the sr object? The sr object is not in scope in ErrHandler so sr.Close() cannot be called. Does the Using block cleanup any resources automatically even if there is an error?

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  • Variable scope and the 'using' statement in .NET

    - by pete the pagan-gerbil
    If a variable is at class level (ie, private MyDataAccessClass _dataAccess;, can it be used as part of a using statement within the methods of that class to dispose of it correctly? Is it wise to use this method, or is it better to always declare a new variable with a using statement (ie, using (MyDataAccessClass dataAccess = new MyDataAccessClass()) instead of using (_dataAccess = new MyDataAccessClass()))?

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  • Disposables, Using & Try/Catch Blocks

    - by Aren B
    Having a mental block today, need a hand verifying my logic isn't fubar'ed. Traditionally I would do file i/o similar to this: FileStream fs = null; // So it's visible in the finally block try { fs = File.Open("Foo.txt", FileMode.Open); /// Do Stuff } catch(IOException) { /// Handle Stuff } finally { if (fs != null) fs.Close(); } However, this isn't very elegant. Ideally I'd like to use the using block to dispose of the filestream when I'm done, however I am unsure about the synergy between using and try/catch. This is how i'd like to implement the above: try { using(FileStream fs = File.Open("Foo.txt", FileMode.Open)) { /// Do Stuff } } catch(Exception) { /// Handle Stuff } However, I'm worried that a premature exit (via thrown exception) from within the using block may not allow the using block to complete execution and clean up it's object. Am I just paranoid, or will this actually work the way I intend it to?

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  • Using statement question

    - by Dan
    I have two questions. 1) Should you always use a using statement on a connection? So, I would use it on the connection and then another one on a reader within the connection? So I would be using two using statements. 2) Lets say you use the using statement on the connection and also a reader being returned on the connection. So you have two using statements. Does it create two Try{}Finally{} blocks or just one? Thanks!

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  • Implementing Linked Lists in C#

    - by nijhawan.saurabh
    Why? The question is why you need Linked Lists and why it is the foundation of any Abstract Data Structure. Take any of the Data Structures - Stacks, Queues, Heaps, Trees; there are two ways to go about implementing them - Using Arrays Using Linked Lists Now you use Arrays when you know about the size of the Nodes in the list at Compile time and Linked Lists are helpful where you are free to add as many Nodes to the List as required at Runtime.   How? Now, let's see how we go about implementing a Simple Linked List in C#. Note: We'd be dealing with singly linked list for time being, there's also another version of linked lists - the Doubly Linked List which maintains two pointers (NEXT and BEFORE).   Class Diagram Let's see the Class Diagram first:     Code     1 // -----------------------------------------------------------------------     2 // <copyright file="Node.cs" company="">     3 // TODO: Update copyright text.     4 // </copyright>     5 // -----------------------------------------------------------------------     6      7 namespace CSharpAlgorithmsAndDS     8 {     9     using System;    10     using System.Collections.Generic;    11     using System.Linq;    12     using System.Text;    13     14     /// <summary>    15     /// TODO: Update summary.    16     /// </summary>    17     public class Node    18     {    19         public Object data { get; set; }    20     21         public Node Next { get; set; }    22     }    23 }    24         1 // -----------------------------------------------------------------------     2 // <copyright file="LinkedList.cs" company="">     3 // TODO: Update copyright text.     4 // </copyright>     5 // -----------------------------------------------------------------------     6      7 namespace CSharpAlgorithmsAndDS     8 {     9     using System;    10     using System.Collections.Generic;    11     using System.Linq;    12     using System.Text;    13     14     /// <summary>    15     /// TODO: Update summary.    16     /// </summary>    17     public class LinkedList    18     {    19         private Node Head;    20     21         public void AddNode(Node n)    22         {    23             n.Next = this.Head;    24             this.Head = n;    25     26         }    27     28         public void printNodes()    29         {    30     31             while (Head!=null)    32             {    33                 Console.WriteLine(Head.data);    34                 Head = Head.Next;    35     36             }    37     38         }    39     }    40 }    41          1 using System;     2 using System.Collections.Generic;     3 using System.Linq;     4 using System.Text;     5      6 namespace CSharpAlgorithmsAndDS     7 {     8     class Program     9     {    10         static void Main(string[] args)    11         {    12             LinkedList ll = new LinkedList();    13             Node A = new Node();    14             A.data = "A";    15     16             Node B = new Node();    17             B.data = "B";    18     19             Node C = new Node();    20             C.data = "C";    21             ll.AddNode(A);    22             ll.AddNode(B);    23             ll.AddNode(C);    24     25             ll.printNodes();    26         }    27     }    28 }    29        Final Words This is just a start, I will add more posts on Linked List covering more operations like Delete etc. and will also explore Doubly Linked List / Implementing Stacks/ Heaps/ Trees / Queues and what not using Linked Lists.   Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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  • What purpose does “using” serve when used the following way

    - by user287745
    What purpose does “using” serve when used the following way:- ONE EXAMPLE IS THIS, (AN ANSWERER- @richj - USED THIS CODE TO SOLVE A PROBLEM THANKS) private Method(SqlConnection connection) { using (SqlTransaction transaction = connection.BeginTransaction()) { try { // Use the connection here .... transaction.Commit(); } catch { transaction.Rollback(); throw; } } } OTHER EXAMPLE I FOUND WHILE READING ON MICROSOFT SUPPORT SITE public static void ShowSqlException(string connectionString) { string queryString = "EXECUTE NonExistantStoredProcedure"; StringBuilder errorMessages = new StringBuilder(); using (SqlConnection connection = new SqlConnection(connectionString)) { SqlCommand command = new SqlCommand(queryString, connection); try { command.Connection.Open(); command.ExecuteNonQuery(); } catch (SqlException ex) { for (int i = 0; i < ex.Errors.Count; i++) { errorMessages.Append("Index #" + i + "\n" + "Message: " + ex.Errors[i].Message + "\n" + "LineNumber: " + ex.Errors[i].LineNumber + "\n" + "Source: " + ex.Errors[i].Source + "\n" + "Procedure: " + ex.Errors[i].Procedure + "\n"); } Console.WriteLine(errorMessages.ToString()); } } } I AM doing at top of page as using system.data.sqlclient etc so why this using thing in middle of code, What if I omit it (I know the code will work) but what functionality will I be losing

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  • Setting article properties for a publication using RMO in C# .NET

    - by Pavan Kumar
    I am using transaction replication with push subscription. I am developing a UI for replication using RMO in C#.NET between different instances of the same database within same machine holding similar schema and structure. I am using Single subscriber and multiple publisher topology. During creation of publication i want to set a few article properties such as Keep the existing object unchanged ,allow schema changes at subscriber to false a,copy foriegn key constarint and copy check constraints to true. How do i set the article properties using RMO in C# .NET. I am using Visual Studio 2008 SP1.I also want to know as how we can select all the objects including Tables,Views,Stored Procedures for publishing at one stretch. I could do it for one table but i want to select all the tables at one stretch. This is the code snippet i used for selecting single table for publishing. TransArticle ta = new TransArticle(); ta.Name = "Article_1"; ta.PublicationName = "TransReplication_DB2"; ta.DatabaseName = "DB2"; ta.SourceObjectName = "person"; ta.SourceObjectOwner = "dbo"; ta.ConnectionContext = conn; ta.Create();

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  • var keyword without 'using someNamespace'

    - by RichK
    How does Visual Studio/intellisense know what to do with a variable declared as var even if you don't include the necessary using declaration at the top? For example, I have class MyDomainObject defined in a different namespace If I don't declare using TheOtherNameSpace; in the file the following code won't compile: private void Foo() { MyDomainObject myObj = new MyDomainObject(); // Doesn't know what this class is } But if I use var var myObj = new MyDomainObject(); This will compile, and intellisense knows exactly what I can with it. So how the heck does it know what the type is without the using? (And as an aside, if it knows without the using, why do we need usings at all?!)

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  • Delayed instantiation with c# using statment

    - by fearofawhackplanet
    Is there any way to write a using statement without instantiating the IDisposable immediately? For example, if I needed to do something like: using (MyThing thing) { if (_config == null) { thing = new MyThing(); } else { thing = new MyThing(_config); } // do some stuff } // end of 'using' Is there an accepted pattern for cases like this? Or am I back to handling the IDisposable explicitly again?

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  • Scope of the c++ using directive

    - by ThomasMcLeod
    From section 7.3.4.2 of the c++11 standard: A using-directive specifies that the names in the nominated namespace can be used in the scope in which the using-directive appears after the using-directive. During unqualified name lookup (3.4.1), the names appear as if they were declared in the nearest enclosing namespace which contains both the using-directive and the nominated namespace. [ Note: In this context, “contains” means “contains directly or indirectly”. —end note ] What do the second and third sentences mean exactly? Please give example. Here is the code I am attempting to understand: namespace A { int i = 7; } namespace B { using namespace A; int i = i + 11; } int main(int argc, char * argv[]) { std::cout << A::i << " " << B::i << std::endl; return 0; } It print "7 7" and not "7 18" as I would expect. Sorry for the typo, the program actually prints "7 11".

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  • What does using mean in c++?

    - by user198729
    Like : using ::size_t; using ::fpos_t; using ::FILE; In fact it's a question inspired by the comment under this question: http://stackoverflow.com/questions/2532412/when-is-h-not-needed-to-include-a-header-file

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