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  • How can I write a null ASCII character (nul) to a file with a Windows batch script?

    - by Matthew Murdoch
    I'm attempting to write an ASCII null character (nul) to a file from a Windows batch script without success. I initially tried using echo like this: echo <Alt+2+5+6> which seems like it should work (typing <Alt+2+5+6> in the command window does write a null character - or ^@ as it appears), but echo then outputs: More? and hangs until I press <Return>. As an alternative I tried using: copy con tmp.txt >nul <Alt+2+5+6><Ctrl+Z> which does exactly what I need, but only if I type it manually in the command window. If I run it from a batch file it hangs until I press <Ctrl+Z> but even then the output file is created but remains empty. I really want the batch file to stand alone without requiring (for example) a separate file containing a null character which can be copied when needed.

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  • Getting Null value with JSON from MySQL, how to retrive data from MySQL to JSON correctly?

    - by sky
    I'm using following code but cannot return data from MySQL. This is the output: <script type="text/javascript"> var somethings= [null,null,null]; </script> It does have three post, but I couldn't get the title(message) output. EDIT: this is the code I'm using: <?php $session = mysql_connect('localhost','name','pass'); mysql_select_db('dbname', $session); $result= mysql_query('SELECT * FROM posts', $session); $somethings= array(); while ($row= mysql_fetch_assoc($result)) { $somethings[]= $row['something']; } ?> <script type="text/javascript"> var somethings= <?php echo json_encode($somethings); ?>; </script> This is the table: message Try iPhone post! Welcome to Yo~ :) ??!

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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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  • Implicit conversion while using += operator?

    - by bdhar
    Conside the following code: int main() { signed char a = 10; a += a; // Line 5 a = a + a; return 0; } I am getting this warning at Line 5: d:\codes\operator cast\operator cast\test.cpp(5) : warning C4244: '+=' : conversion from 'int' to 'signed char', possible loss of data Does this mean that += operator makes an implicit cast of the right hand operator to int? P.S: I am using Visual studio 2005

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  • Null Value Statement

    - by Sam
    Hi All, I have created a table called table1 and it has 4 columns named Name,ID,Description and Date. I have created them like Name varchar(50) null, ID int null,Description varchar(50) null, Date datetime null I have inserted a record into the table1 having ID and Description values. So Now my table1 looks like this: Name ID Description Date Null 1 First Null One of them asked me to modify the table such a way that The columns Name and Date should have Null values instead of Text Null. I don't know what is the difference between those I mean can anyone explain me the difference between these select statements: SELECT * FROM TABLE1 WHERE NAME IS NULL SELECT * FROM TABLE1 WHERE NAME = 'NULL' SELECT * FROM TABLE1 WHERE NAME = ' ' Can anyone explain me?

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  • Automapper: Handling NULL members

    - by PSteele
    A question about null members came up on the Automapper mailing list.  While the problem wasn’t with Automapper, investigating the issue led to an interesting feature in Automapper. Normally, Automapper ignores null members.  After all, what is there really to do?  Imagine these source classes: public class Source { public int Data { get; set; } public Address Address { get; set; } }   public class Destination { public string Data { get; set; } public Address Address { get; set; } }   public class Address { public string AddressType { get; set; } public string Location { get; set; } } And imagine a simple mapping example with these classes: Mapper.CreateMap<Source, Destination>();   var source = new Source { Data = 22, Address = new Address { AddressType = "Home", Location = "Michigan", }, };   var dest = Mapper.Map<Source, Destination>(source); The variable ‘dest’ would have a complete mapping of the Data member and the Address member. But what if the source had no address? Mapper.CreateMap<Source, Destination>();   var source = new Source { Data = 22, };   var dest = Mapper.Map<Source, Destination>(source); In that case, Automapper would just leave the Destination.Address member null as well.  But what if we always wanted an Address defined – even if it’s just got some default data?  Use the “NullSubstitute” option: Mapper.CreateMap<Source, Destination>() .ForMember(d => d.Address, o => o.NullSubstitute(new Address { AddressType = "Unknown", Location = "Unknown", }));   var source = new Source { Data = 22, };   var dest = Mapper.Map<Source, Destination>(source); Now, the ‘dest’ variable will have an Address defined with a type and location of “Unknown”.  Very handy! Technorati Tags: .NET,Automapper,NULL

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  • Problems with subversion (in gnome keyring, maybe), user=null

    - by Tom Brito
    I'm having a problem with my subversion in Ubuntu, and it's happening only on my computer, my colleagues are working fine. It asks for password for user "(null)": Password for '(null)' GNOME keyring: entering the password it shows: svn: OPTIONS of 'http://10.0.203.3/greenfox': authorization failed: Could not authenticate to server: rejected Basic challenge (http://10.0.203.3) What can be causing that (again: it's just on my computer, the svn server is ok).

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  • Adding Column to a SQL Server Table

    - by Dinesh Asanka
    Adding a column to a table is  common task for  DBAs. You can add a column to a table which is a nullable column or which has default values. But are these two operations are similar internally and which method is optimal? Let us start this with an example. I created a database and a table using following script: USE master Go --Drop Database if exists IF EXISTS (SELECT 1 FROM SYS.databases WHERE name = 'AddColumn') DROP DATABASE AddColumn --Create the database CREATE DATABASE AddColumn GO USE AddColumn GO --Drop the table if exists IF EXISTS ( SELECT 1 FROM sys.tables WHERE Name = 'ExistingTable') DROP TABLE ExistingTable GO --Create the table CREATE TABLE ExistingTable (ID BIGINT IDENTITY(1,1) PRIMARY KEY CLUSTERED, DateTime1 DATETIME DEFAULT GETDATE(), DateTime2 DATETIME DEFAULT GETDATE(), DateTime3 DATETIME DEFAULT GETDATE(), DateTime4 DATETIME DEFAULT GETDATE(), Gendar CHAR(1) DEFAULT 'M', STATUS1 CHAR(1) DEFAULT 'Y' ) GO -- Insert 100,000 records with defaults records INSERT INTO ExistingTable DEFAULT VALUES GO 100000 Before adding a Column Before adding a column let us look at some of the details of the database. DBCC IND (AddColumn,ExistingTable,1) By running the above query, you will see 637 pages for the created table. Adding a Column You can add a column to the table with following statement. ALTER TABLE ExistingTable Add NewColumn INT NULL Above will add a column with a null value for the existing records. Alternatively you could add a column with default values. ALTER TABLE ExistingTable Add NewColumn INT NOT NULL DEFAULT 1 The above statement will add a column with a 1 value to the existing records. In the below table I measured the performance difference between above two statements. Parameter Nullable Column Default Value CPU 31 702 Duration 129 ms 6653 ms Reads 38 116,397 Writes 6 1329 Row Count 0 100000 If you look at the RowCount parameter, you can clearly see the difference. Though column is added in the first case, none of the rows are affected while in the second case all the rows are updated. That is the reason, why it has taken more duration and CPU to add column with Default value. We can verify this by several methods. Number of Pages The number of data pages can be obtained by using DBCC IND command. Though, this an undocumented dbcc command, many experts are ok to use this command in production. However, since there is no official word from Microsoft, use this “at your own risk”. DBCC IND (AddColumn,ExistingTable,1) Before Adding the Columns 637 Adding a Column with NULL 637 Adding a column with DEFAULT value 1270 This clearly shows that pages are physically modified. Please note, a high value indicated in the Adding a column with DEFAULT value  column is also a result of page splits. Continues…

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  • Save programmatically created Mesh to .X Files using SlimDX throw null exception

    - by zionpi
    Mesh has been created properly using SlimDX,but when I use the following line: Mesh.ToXFile(barMesh, "foo.x", XFileFormat.Text,CharSet.Unicode); It throws NullReferenceException,through monitor window I can see barMesh is not null, inside the mesh structrue, SkinInfo is null. If SkinInfo is the problem,then how can I initialize it properly?Internet doesn't seems have much information on this.

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  • Is it possible that an insert would use parallelism?

    - by Lieven Cardoen
    In what situation can inserting a simple record (the table has got some 10 columns, two of them are xml) use parallelism? CREATE TABLE [dbo].[PackageSessions]( [PackageSessionId] [int] IDENTITY(1,1) NOT NULL, [PackageId] [int] NOT NULL, [UserId] [int] NOT NULL, [StartDateTime] [datetime] NULL, [StopDateTime] [datetime] NULL, [Score] [float] NOT NULL, [ScoreMax] [float] NOT NULL, [CompletionStatus] [int] NOT NULL, [ReviewPlayerContextId] [int] NOT NULL, [PlayerContextId] [int] NOT NULL, [ReducedScore] [float] NOT NULL, [ReducedScoreMax] [float] NOT NULL, [PackageSnapShot] [xml] NULL, [InterfaceLanguageId] [int] NOT NULL, [Data] [xml] NULL, [PackageSessionLanguageId] [int] NOT NULL, CONSTRAINT [PackageSessions_PK] PRIMARY KEY CLUSTERED ( [PackageSessionId] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY]

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  • Avoiding new operator in JavaScript -- the better way

    - by greengit
    Warning: This is a long post. Let's keep it simple. I want to avoid having to prefix the new operator every time I call a constructor in JavaScript. This is because I tend to forget it, and my code screws up badly. The simple way around this is this... function Make(x) { if ( !(this instanceof arguments.callee) ) return new arguments.callee(x); // do your stuff... } But, I need this to accept variable no. of arguments, like this... m1 = Make(); m2 = Make(1,2,3); m3 = Make('apple', 'banana'); The first immediate solution seems to be the 'apply' method like this... function Make() { if ( !(this instanceof arguments.callee) ) return new arguments.callee.apply(null, arguments); // do your stuff } This is WRONG however -- the new object is passed to the apply method and NOT to our constructor arguments.callee. Now, I've come up with three solutions. My simple question is: which one seems best. Or, if you have a better method, tell it. First – use eval() to dynamically create JavaScript code that calls the constructor. function Make(/* ... */) { if ( !(this instanceof arguments.callee) ) { // collect all the arguments var arr = []; for ( var i = 0; arguments[i]; i++ ) arr.push( 'arguments[' + i + ']' ); // create code var code = 'new arguments.callee(' + arr.join(',') + ');'; // call it return eval( code ); } // do your stuff with variable arguments... } Second – Every object has __proto__ property which is a 'secret' link to its prototype object. Fortunately this property is writable. function Make(/* ... */) { var obj = {}; // do your stuff on 'obj' just like you'd do on 'this' // use the variable arguments here // now do the __proto__ magic // by 'mutating' obj to make it a different object obj.__proto__ = arguments.callee.prototype; // must return obj return obj; } Third – This is something similar to second solution. function Make(/* ... */) { // we'll set '_construct' outside var obj = new arguments.callee._construct(); // now do your stuff on 'obj' just like you'd do on 'this' // use the variable arguments here // you have to return obj return obj; } // now first set the _construct property to an empty function Make._construct = function() {}; // and then mutate the prototype of _construct Make._construct.prototype = Make.prototype; eval solution seems clumsy and comes with all the problems of "evil eval". __proto__ solution is non-standard and the "Great Browser of mIsERY" doesn't honor it. The third solution seems overly complicated. But with all the above three solutions, we can do something like this, that we can't otherwise... m1 = Make(); m2 = Make(1,2,3); m3 = Make('apple', 'banana'); m1 instanceof Make; // true m2 instanceof Make; // true m3 instanceof Make; // true Make.prototype.fire = function() { // ... }; m1.fire(); m2.fire(); m3.fire(); So effectively the above solutions give us "true" constructors that accept variable no. of arguments and don't require new. What's your take on this. -- UPDATE -- Some have said "just throw an error". My response is: we are doing a heavy app with 10+ constructors and I think it'd be far more wieldy if every constructor could "smartly" handle that mistake without throwing error messages on the console.

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  • Drop Down list null value not working for selected text c#?

    - by Tamara JQ
    Hi guys, Basically I have a drop down list which is populated with text and values depending on a selected index of a radio button list. The code is as follows: protected void RBLGender_SelectedIndexChanged(object sender, EventArgs e) { DDLTrous.Items.Clear(); DDLShoes.Items.Clear(); if (RBLGender.SelectedValue.Equals("Male")) { String[] MaleTrouserText = {"[N/A]", "28\"", "30\"", "32\"", "34\"", "36\"", "38\"", "40\"", "42\"", "44\"", "48\""}; String[] MaleTrouserValue = { null, "28\"", "30\"", "32\"", "34\"", "36\"", "38\"", "40\"", "42\"", "44\"", "48\"" }; String[] MaleShoeText = { "[N/A]", "38M", "39M", "40M", "41M", "42M", "43M", "44M", "45M", "46M", "47M" }; String[] MaleShoeValue = { null, "38M", "39M", "40M", "41M", "42M", "43M", "44M", "45M", "46M", "47M" }; for (int i = 0; i < MaleTrouserText.Length; i++) { ListItem MaleList = new ListItem(MaleTrouserText[i], MaleTrouserValue[i]); DDLTrous.Items.Add(MaleList); } for (int i = 0; i < MaleShoeText.Length; i++) { ListItem MaleShoeList = new ListItem(MaleShoeText[i], MaleShoeValue[i]); DDLShoes.Items.Add(MaleShoeList); } } else if (RBLGender.SelectedValue.Equals("Female"))` When the text '[N/A]' is selected I want the value NULL to be inserted into the database. At present when '[N/A]' is selected the value entered into the database is [N/A] does anyone know why? Thanks in advance.

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  • PostGres Error When Using Distinct : postgres ERROR: could not identify an ordering operator for ty

    - by CaffeineIV
    ** EDIT ** Nevermind, just needed to take out the parens... I get this error: ERROR: could not identify an ordering operator for type record when trying to use DISTINCT Here's the query: select DISTINCT(g.fielda, g.fieldb, r.type) from fields g LEFT JOIN types r ON g.id = r.id; And the errors: ERROR: could not identify an ordering operator for type record HINT: Use an explicit ordering operator or modify the query. ********** Error ********** ERROR: could not identify an ordering operator for type record SQL state: 42883 Hint: Use an explicit ordering operator or modify the query.

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  • Recognizing when to use the mod operator

    - by Will
    I have a quick question about the mod operator. I know what it does; it calculates the remainder of a division. My question is, how can I identify a situation where I would need to use the mod operator? I know I can use the mod operator to see whether a number is even or odd and prime or composite, but that's about it. I don't often think in terms of remainders. I'm sure the mod operator is useful and I would like to learn to take advantage of it. I just have problems identifying where the mod operator is applicable. In various programming situations, it is difficult for me to see a problem and realize "hey! the remainder of division would work here!" Any tips or strategies? Thanks

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  • Can a WPF ComboBox display alternative text when its selection is null?

    - by Garth T Kidd
    G'day! I want my WPF ComboBox to display some alternative text when its data-bound selection is null. The view model has the expected properties: public ThingoSelectionViewModel : INotifyPropertyChanged { public ThingoSelectionViewModel(IProvideThingos) { this.Thingos = IProvideThingos.GetThingos(); } public ObservableCollection<Thingo> Thingos { get; set; } public Thingo SelectedThingo { get { return this.selectedThingo; } set { // set this.selectedThingo and raise the property change notification } // ... } The view has XAML binding to the view model in the expected way: <ComboBox x:Name="ComboboxDrive" SelectedItem="{Binding Path=SelectedThingo}" IsEditable="false" HorizontalAlignment="Left" MinWidth="100" IsReadOnly="false" Style="{StaticResource ComboboxStyle}" Grid.Column="1" Grid.Row="1" Margin="5" SelectedIndex="0"> <ComboBox.ItemsSource> <CompositeCollection> <ComboBoxItem IsEnabled="False">Select a thingo</ComboBoxItem> <CollectionContainer Collection="{Binding Source={StaticResource Thingos}}" /> </CompositeCollection> </ComboBox.ItemsSource> </ComboBox> The ComboBoxItem wedged into the top is a way to get an extra item at the top. It's pure chrome: the view model stays pure and simple. There's just one problem: the users want "Select a thingo" displayed whenever the ComboBox' selection is null. The users do not want a thingo selected by default. They want to see a message telling them to select a thingo. I'd like to avoid having to pollute the viewmodel with a ThingoWrapper class with a ToString method returning "Select a thingo" if its .ActualThingo property is null, wrapping each Thingo as I populate Thingos, and figuring out some way to prevent the user from selecting the nulled Thingo. Is there a way to display "Select a thingo" within the ComboBox' boundaries using pure XAML, or pure XAML and a few lines of code in the view's code-behind class?

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  • Matching the superclass's constructor's parameter list, is treating a null default value as a non-null value within a constructor a violation of LSP?

    - by Panzercrisis
    I kind of ran into this when messing around with FlashPunk, and I'm going to use it as an example. Essentially the main sprite class is pretty much class Entity. Entity's constructor has four parameters, each with a default value. One of them is graphic, whose default value is null. Entity is designed to be inherited from, with many such subclasses providing their own graphic within their own internal workings. Normally these subclasses would not have graphic in their constructor's parameter lists, but would simply pick something internally and go with it. However I was looking into possibly still adhering to the Liskov Substitution Principal. Which led me to the following example: package com.blank.graphics { import net.flashpunk.*; import net.flashpunk.graphics.Image; public class SpaceGraphic extends Entity { [Embed(source = "../../../../../../assets/spaces/blank.png")] private const BLANK_SPACE:Class; public function SpaceGraphic(x:Number = 0, y:Number = 0, graphic:Graphic = null, mask:Mask = null) { super(x, y, graphic, mask); if (!graphic) { this.graphic = new Image(BLANK_SPACE); } } } } Alright, so now there's a parameter list in the constructor that perfectly matches the one in the super class's constructor. But if the default value for graphic is used, it'll exhibit two different behaviors, depending on whether you're using the subclass or the superclass. In the superclass, there won't be a graphic, but in the subclass, it'll choose the default graphic. Is this a violation of the Liskov Substitution Principal? Does the fact that subclasses are almost intended to use different parameter lists have any bearing on this? Would minimizing the parameter list violate it in a case like this? Thanks.

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