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ViewState Extension Method
How many times have you written something like this?
public string MyStringProperty
{
  get
  {
    object s = ViewState["MyStringProperty"];
    if( s == null )
    {
      s = "MyDefaultValue";
    }

    return (String)s;
  }

  set { ViewState["MyStringProperty"] = value; }
}

public bool MyBooleanProperty
{
  get
  {
    object b = ViewState["MyBooleanProperty"];
    if( b == null )
    {
      b = true;
    }

    return (bool)b;
  }

  set { ViewState["MyBooleanProperty"] = value; }
}
Wouldn't this be better?
public string MyStringProperty
{
  get { return ViewState.GetValue("MyStringProperty", "MyDefaultValue"); }
  set { ViewState["MyStringProperty"] = value; }
}

public bool MyBooleanProperty
{
  get { return ViewState.GetValue("MyBooleanProperty", true ); }
  set { ViewState["MyBooleanProperty"] = value; }
}
With C# 3.5, all you need is this extension method
internal static class MyExtensions
{
  public static T GetValue<T>(this IDictionary bag, string key, T defaultValue )
  {
    object value = bag[key];
    if( value == null )
    {
      value = defaultValue;
    }

    return (T)value;
}
Cheers
posted on Monday, March 10, 2008 1:44 PM
Filed Under [ .Net ASP.Net C# ]

Comments

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# re: ViewState Extension Method
posted by Dana Hanna
on 4/17/2008 12:33 PM
This shows typical over use of extension methods.

Lookup the C# operator "??". It does what you want, no extension method needed.

object s = ViewState["MyStringProperty"] ?? "MyDefaultValue";
Gravatar
# re: ViewState Extension Method
posted by Will Smith
on 4/17/2008 3:56 PM
Not exactly. More like ignorance of the compiler directives/operators.

Plus, I've extended this concept further to accept a delegate that returns the type I want, and optionally updates the dictionary with the new value. Not the typical pattern you would see with viewstate, but I've applied this to HttpRuntime.Cache as well.

Take a look at my More Fun With Extension Methods post.
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# re: ViewState Extension Method
posted by Thurein
on 10/4/2008 11:37 AM
I like your extension method. It would be much helpful. If you allow me, I would like to modify in this way:

internal static class MyExtensions
{
public static T GetValue<T>(this IDictionary bag, string key, T defaultValue )
{
object value = bag[key] ?? defaultValue;

return (T)value;
}
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