C# tip use Dictionary TryGetValue

Taswar Bhatti February 10, 2014 No Comments

Here is another C# tip.
Most of the time when you are trying to get a value from dictionary you would try to check if the key exist or not something like.

if(dictionary.ContainsKey(key))
{
  var value - dictionary[key];
 //do some stuff

}

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if(dictionary.ContainsKey(key))

{

var value - dictionary[key];

//do some stuff

}

But one can use TryGetValue

if(dictionary.TryGetValue(key, out value))
{
  //do stuff with value
}

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if(dictionary.TryGetValue(key, out value))

{

//do stuff with value

}

The benefit of using TryGetValue is that the dictionary is synchronized, there is no race condition.

.NET, C#

.net, C#, csharp, dotnet

WPF DataTemplate bind property to Parent ViewModel

Taswar Bhatti January 10, 2014 No Comments

Here is a hint when using WPF and you may come into a situation where you want to databind an element to its Parent ViewModel.

As an example lets say you have a view that is binding to ViewModel and inside your xaml you have a control that has DataTemplate
The code Below we are using the BusyIndicator from https://wpftoolkit.codeplex.com/

<xctk:BusyIndicator.BusyContentTemplate>
            <DataTemplate>
                 <StackPanel Margin="4">
                          &lt;TextBlock Text="{Binding MyProcessText}" FontWeight="Bold" HorizontalAlignment="Center"/>
            </DataTemplate>
</xctk:BusyIndicator.BusyContentTemplate>
</xctk:BusyIndicator>

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<xctk:BusyIndicator.BusyContentTemplate>

</DataTemplate>

</xctk:BusyIndicator.BusyContentTemplate>

</xctk:BusyIndicator>

Our ViewModel looks like

public class ViewModel
{
  private string _text;
  public string MyProcessText { 
   get {return _text; }
   set { _text = value; RaisePropertyChanged("MyProcessText"); }
}

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public class ViewModel

{

private string _text;

public string MyProcessText {

get {return _text; }

set { _text = value; RaisePropertyChanged("MyProcessText"); }

}

We would assume that the property would bind, but actually it doesn’t since the datatemplate is there.

So what we need to do is bind it to its parent viewmodel

What we need to provide is RelativeSource and the AncestorType, below we are using UserControl but it could also be Window or a provided type like AncestorType={x:Type XYZObject}

&lt;TextBlock Text="{Binding MyProcessText, RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl}" FontWeight="Bold" HorizontalAlignment="Center"/>

1	<TextBlock Text="{Binding MyProcessText, RelativeSource={RelativeSource FindAncestor, AncestorType=UserControl}" FontWeight="Bold" HorizontalAlignment="Center"/>

.NET, C#, WPF

.net, C#, csharp, dotnet, WPF

IIS8 HTTP Error 500.19 – Internal Server Error

Taswar Bhatti December 19, 2013 No Comments

If you are running Windows Server 2012 with IIS8 and you got this error HTTP Error 500.19 – Internal Server Error. If you web.config file contains “handler” or “modules” tag.

In order to fix this, launch cmd or powershell and execute these 2 commands inside of C:\Windows\System32\InetSrv

PS C:\Windows\System32\InetSrv>.\appcmd.exe unlock config -section:system.webServer/handlers

PS C:\Windows\System32\InetSrv> .\appcmd unlock config -section:system.webServer/modules

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PS C:\Windows\System32\InetSrv>.\appcmd.exe unlock config -section:system.webServer/handlers

PS C:\Windows\System32\InetSrv> .\appcmd unlock config -section:system.webServer/modules

This will unlock the handlers and modules section.

.NET, ASP .NET

IIS

C# tip: use params for method that takes variable number of arguments

Taswar Bhatti December 16, 2013 No Comments

In C# there is a params keyword which allows a method parameter to take variable number of arguments. MSDN

Some notes on param

It must always be the last parameter in the function/method definition
There can only be one params keyword in a function/method parameter signature

Example:

int Sum(int[] args)
{
  int sum = 0;
  foreach (var item in args)
  {
    sum += item;
  }

  return sum;
}

//calling the above Sum method we would call it like
int[] array = new int[] {1, 2, 3}
int result = Sum(array);

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int Sum(int[] args)

{

int sum = 0;

foreach (var item in args)

{

sum += item;

}

return sum;

}

//calling the above Sum method we would call it like

int[] array = new int[] {1, 2, 3}

int result = Sum(array);

But by changing it to params we can change the call and simplify it

int SumWithParams(params int[] args)
{
  int sum = 0;
  foreach (var item in args)
  {
    sum += item;
  }

  return sum;
}

//calling the above SumWithParams  woud give us the same result
int result = SumWithParams(1, 2, 3);

//calling this would not fail either
int result = SumWithParams(); //result is 0

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int SumWithParams(params int[] args)

{

int sum = 0;

foreach (var item in args)

{

sum += item;

}

return sum;

}

//calling the above SumWithParams woud give us the same result

int result = SumWithParams(1, 2, 3);

//calling this would not fail either

int result = SumWithParams(); //result is 0

There is no performance bottleneck in using params because the compiler is basically changing your code into an array for you, thus it is basically just syntactic sugar for C#.

.NET, C#

.net, C#, csharp, dotnet

Phantomjs talk in Ottawa JS Meetup

Taswar Bhatti December 12, 2013 No Comments

Thanks to everyone who came out last night at OttawaJS for the phantomjs talk, the slides are located at slid.es.
You can find the code in my github account. https://github.com/taswar/ottawajs-dec2013

A recap of things we covered:

Simple screencapture
CoffeeScript with phantomjs
Scraping hackernews and dzone site for links
using webdriver to integrate with phantomjs (python and ruby)
Using remote webdriver to integrate phantomjs with jruby
Rails app with phantomjs integrated to take screencapture

Links, Misc

Javascript, Jruby, ottawajs, phantomjs, talk

C# tip: out parameter keyword

Taswar Bhatti December 11, 2013 No Comments

In C# there is the out parameter keyword which causes arguments to be passed by reference. It is like the ref keyword, except that ref requires that the variable be initialized before it is passed.

Example:

void Init(out int x)
{
 x = 47;
}

int x;

Init(out x);

Console.WriteLine(x); //x now is 47

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void Init(out int x)

{

x = 47;

}

int x;

Init(out x);

Console.WriteLine(x); //x now is 47

The out parameter keyword provides a way for a method to output multiple values from a method without using an array or object, since the return statement only allows one output, by using out one can return multiple values.

bool HasComma(string str, out string data)
{
	if(str.Contains(','))
	{
	  int index = str.LastIndexOf(',') + 1;	  
	  data = str.Substring(index);
	  return true;
	}
	
	data = string.Empty;
	return false;
}

string d;
bool containsComma = HasComma("a,B",out  d);
Console.WriteLine(d); //d is now the string B containsComma is true
	
containsComma = HasComma("ab",out  d); //d is string.Empty and containsComma is false

int a, b, c, d, e;
bool isTrue = Method(out a, out b, out c, out d, out e); // bad method.

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bool HasComma(string str, out string data)

{

if(str.Contains(','))

{

int index = str.LastIndexOf(',') + 1;

data = str.Substring(index);

return true;

}

data = string.Empty;

return false;

}

string d;

bool containsComma = HasComma("a,B",out d);

Console.WriteLine(d); //d is now the string B containsComma is true

containsComma = HasComma("ab",out d); //d is string.Empty and containsComma is false

int a, b, c, d, e;

bool isTrue = Method(out a, out b, out c, out d, out e); // bad method.

Last but not least I personally do not recommend using out keyword and also from
The Framework Design Guidelines it also recommend to avoid using out. If you have multiple returns use an object that wraps around the value is a better design.

.NET, C#

.net, C#, csharp, dotnet

C# the use of ref keyword

Taswar Bhatti December 6, 2013 No Comments

In C# when using the ref keyword it causes an argument to be passed by reference, not by value.
In order to use a ref as a parameter, both the method definition and the calling method must explicitly use the ref keyword, and also the variable must be initialized before passing in.

In the example below we have two methods, one using the ref keyword the other not.

void Increment(int x)
{
  x = x + 1;
}


void IncrementWithRef(ref int y)
{
  y = y + 1;
}

int x = 1;
Increment(x); 

Console.WriteLine(x);//x is still 1

Increment(ref x);
Console.WriteLine(x);//x is now 2

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void Increment(int x)

{

x = x + 1;

}

void IncrementWithRef(ref int y)

{

y = y + 1;

}

int x = 1;

Increment(x);

Console.WriteLine(x);//x is still 1

Increment(ref x);

Console.WriteLine(x);//x is now 2

But what about objects that are reference types. Here is where the confusion starts that the concept of passing by reference with the concept of reference types, the concepts are not the same. A method parameter can pass in a ref type regardless of its type (value or reference).

Below is an example that shows when a Person object reference type is used.

public class Person
{
  public string Name { get; set; }
}

void NameChange(Person p)
{
   p.Name = "John";
}

void NameChangeRef(ref Person p)
{
 p = new Person{ Name = "Ref Person" };
}

Person p = new Person { Name = "Peter" };
	
Console.WriteLine(p.Name); //output is Peter
	
NameChange(p);
	
Console.WriteLine(p.Name); //output is John we have changed the reference type property but not the object
	
NameChangeRef(ref p); 
	
Console.WriteLine(p.Name); //output is Ref Person we have changed the object that p points to

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public class Person

{

public string Name { get; set; }

}

void NameChange(Person p)

{

p.Name = "John";

}

void NameChangeRef(ref Person p)

{

p = new Person{ Name = "Ref Person" };

}

Person p = new Person { Name = "Peter" };

Console.WriteLine(p.Name); //output is Peter

NameChange(p);

Console.WriteLine(p.Name); //output is John we have changed the reference type property but not the object

NameChangeRef(ref p);

Console.WriteLine(p.Name); //output is Ref Person we have changed the object that p points to

Last but not least I personally do not recommend using ref keyword and also from
The Framework Design Guidelines it also recommend to avoid using ref.

.NET, C#

.net, C#, csharp, dotnet

C# tip: Use Path Combine for file or directory path information

Taswar Bhatti December 4, 2013 1 Comment

.NET provides in its System.IO namespace the Path class which performs operations on String instances that contain file or directory path information. These operations are performed in a cross-platform manner.

Most of the time we see develeopers writing code like

string path = somePath + "\\" + filename;

1	string path = somePath + "\\" + filename;

But by using Path.Combine we can provide a cross platform path

string somePath = @"C:\temp";
string filename = "dat.txt";
string path = Path.Combine(somePath,filename);

//produce an output of C:\temp\dat.txt
//linux: C:/temp/dat.txt

string[] paths = {@"c:\My Music", "2013", "media", "banner"};
string fullPath = Path.Combine(paths);
//output c:\My Music\2013\media\banner

string path1 = @"C:\Temp";
string path2 = "My Music";
fullPath = Path.Combine(path1, path2);

//output: C:\Temp\My Music

fullPath = Path.Combine(string.Empty, path2);
//output: My Music
	
fullPath = Path.Combine(path1, string.Empty);
//output: C:\Temp

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string somePath = @"C:\temp";

string filename = "dat.txt";

string path = Path.Combine(somePath,filename);

//produce an output of C:\temp\dat.txt

//linux: C:/temp/dat.txt

string[] paths = {@"c:\My Music", "2013", "media", "banner"};

string fullPath = Path.Combine(paths);

//output c:\My Music\2013\media\banner

string path1 = @"C:\Temp";

string path2 = "My Music";

fullPath = Path.Combine(path1, path2);

//output: C:\Temp\My Music

fullPath = Path.Combine(string.Empty, path2);

//output: My Music

fullPath = Path.Combine(path1, string.Empty);

//output: C:\Temp

By using the Path and Combine method, one can at least eliminate some of the headache of porting to another platform.

.NET, C#

.net, C#, csharp, dotnet

Documentation comment your C# code use GhostDoc at least

Taswar Bhatti December 2, 2013 No Comments

Recently have been going through some old code to review the comments in them from other developers and what I find out is developers tend to have really bad comments & documentation in their code

Example:

public class Person 
{
   /// &lt;summary>
   /// Constructor
   /// &lt;/summary>
   public Person() {}
   
}

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public class Person

{

/// <summary>

/// Constructor

/// </summary>

public Person() {}

}

From the above code it is obvious that it is the constructor but does the comment tell me anything? I understand that sometimes it may be hard to document or comment certain method, thus I really strongly suggest at least use GhostDoc

What is GhostDoc?
GhostDoc is a Visual Studio extension that automatically generates XML documentation comments for methods and properties based on their type, parameters, name, and other contextual information.

Here is the result of using GhostDoc on the Person Class

public class Person 
{
   /// &lt;summary>
   /// Initializes a new instance of the &lt;see cref="Person"/> class.
   /// &lt;/summary>
   public Person() {}   
}

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public class Person

{

/// <summary>

/// Initializes a new instance of the <see cref="Person"/> class.

/// </summary>

public Person() {}

}

As one can see Ghostdoc does a better job, don’t get me wrong GhostDoc still requires one to go through the comments here is an example where it tries to make sense.

 /// &lt;summary>
 /// Riches the text selection changed.
 /// &lt;/summary>
 /// &lt;param name="richTextBox">The rich text box.&lt;/param>
 private void RichTextSelection_Changed(System.Windows.Controls.RichTextBox richTextBox)

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/// <summary>

/// Riches the text selection changed.

/// </summary>

/// <param name="richTextBox">The rich text box.</param>

private void RichTextSelection_Changed(System.Windows.Controls.RichTextBox richTextBox)

Riches the text selection changed. ????? As you can see it didn’t do one of the best job for this comment, but at least one can modify it and it may become “RichTextBox selection has changed event handler”

Personally I would recommend using the tool but just take it with a grain of salt and always check the documentation that it generates.

.NET, C#, Misc

.net, C#, csharp, dotnet

LINQ tip – Ordering collection using existing array/collection using OrderBy

Taswar Bhatti November 29, 2013 5 Comments

Here is a LINQ tip where you may wish to order a collection with an existing ordering of another collection.

Example:

int[] displaySeq = new int[] { 1, 8, 5, 7, 13 }; //the ordering we want at the end

//collection that we will be sorting on
List<Person> people = new List<Person>();
people.Add(new Person { DisplaySeq = 5});
people.Add(new Person { DisplaySeq = 13});
people.Add(new Person { DisplaySeq = 7});
people.Add(new Person { DisplaySeq = 1});
people.Add(new Person { DisplaySeq = 8});

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int[] displaySeq = new int[] { 1, 8, 5, 7, 13 }; //the ordering we want at the end

//collection that we will be sorting on

List<Person> people = new List<Person>();

people.Add(new Person { DisplaySeq = 5});

people.Add(new Person { DisplaySeq = 13});

people.Add(new Person { DisplaySeq = 7});

people.Add(new Person { DisplaySeq = 1});

people.Add(new Person { DisplaySeq = 8});

Currently as it stands our data is stored in the order of { 5, 13, 7, 1, 8 } and we wish to order them in terms of { 1, 8, 5, 7, 13 }, we can use LINQ OrderBy to do so.

//use the displaySeq array and find the index of it
var sorted = people.OrderBy(x => { return Array.IndexOf(displaySeq, x.DisplaySeq); }).ToList();

1 2	//use the displaySeq array and find the index of it var sorted = people.OrderBy(x => { return Array.IndexOf(displaySeq, x.DisplaySeq); }).ToList();

By doing so we end up with { 1, 8, 5, 7, 13 }, now if we wanted to put elements that dont have matching at the end of the list we can modify the OrderBy like this.

//add another person that is not part of the displaySeq array
people.Add(new Person { DisplaySeq = 99});

var sorted = people.OrderBy(x => { 
   var index = Array.IndexOf(displaySeq, x.DisplaySeq);
   return index < 0 ? int.MaxValue : index;
 }).ToList();

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//add another person that is not part of the displaySeq array

people.Add(new Person { DisplaySeq = 99});

var sorted = people.OrderBy(x => {

var index = Array.IndexOf(displaySeq, x.DisplaySeq);

return index < 0 ? int.MaxValue : index;

}).ToList();

.NET, C#

.net, C#, csharp, dotnet, LINQ

C# tip use Dictionary TryGetValue

WPF DataTemplate bind property to Parent ViewModel

IIS8 HTTP Error 500.19 – Internal Server Error

C# tip: use params for method that takes variable number of arguments

Phantomjs talk in Ottawa JS Meetup

C# tip: out parameter keyword

C# the use of ref keyword

C# tip: Use Path Combine for file or directory path information

Documentation comment your C# code use GhostDoc at least

LINQ tip – Ordering collection using existing array/collection using OrderBy

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