利用MS AJAX擴充伺服器端控制項

通過MS AJAX可以擴充一個伺服器端控制項在用戶端轉譯後的特性，使其介面更加友好。
執行個體代碼:IScriptControl.rar
一、建立網站，選擇ASP.NET AJAX-Enabled Web Site.
二、向項目中添加一個類，使其派生自TextBox，並實現IScriptControl介面。如下代碼執行個體：

public class SampleTextBox : TextBox, IScriptControl

三、這個控制項我們將實現兩個屬性：
HighlightCSSClass 控制項得到焦點後的樣式。當控制項得到焦點的時候使其能夠高亮顯示。
NoHighlightCssClass 失去焦點的控制項的樣式。

public string HighlightCssClass
{
get { return _highlightCssClass; }
set { _highlightCssClass = value; }
}

public string NoHighlightCssClass
{
get { return _noHighlightCssClass; }
set { _noHighlightCssClass = value; }
}

四、介面IScriptControl 的實現。
GetScriptDescriptors() 返回一個包含控制項用戶端執行個體的屬性和事件控制代碼的 ScriptDescriptor 類型的數組。
GetScriptReferences() 返回一個包含控制項用戶端 javascript 代碼的ScriptReference 類型的數組。
在這個執行個體中，我們用四個函數來實現這兩個函數。代碼入下：
protected virtual IEnumerable<ScriptReference> GetScriptReferences()
{
ScriptReference reference = new ScriptReference();
reference.Path = ResolveClientUrl("SampleTextBox.js");

return new ScriptReference[] { reference };
}

protected virtual IEnumerable<ScriptDescriptor> GetScriptDescriptors()
{
ScriptControlDescriptor descriptor = new ScriptControlDescriptor("Samples.SampleTextBox", this.ClientID);
descriptor.AddProperty("highlightCssClass", this.HighlightCssClass);
descriptor.AddProperty("nohighlightCssClass", this.NoHighlightCssClass);

return new ScriptDescriptor[] { descriptor };
}

IEnumerable<ScriptReference> IScriptControl.GetScriptReferences()
{
return GetScriptReferences();
}

IEnumerable<ScriptDescriptor> IScriptControl.GetScriptDescriptors()
{
return GetScriptDescriptors();
} 五、這冊控制項。代碼比較簡單，所以就不再多加講述，入下：
protected override void OnPreRender(EventArgs e)
{
if (!this.DesignMode)
{
// Test for ScriptManager and register if it exists
sm = ScriptManager.GetCurrent(Page);

if (sm == null)
throw new HttpException("A ScriptManager control must exist on the current page.");

sm.RegisterScriptControl(this);
}

base.OnPreRender(e);
}

protected override void Render(HtmlTextWriter writer)
{
if (!this.DesignMode)
sm.RegisterScriptDescriptors(this);

base.Render(writer);
}
六、下邊是我們新添加的類的完整代碼：
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Collections.Generic;

namespace TextBoxExtender
{
/**//// <summary>
/// SampleTextBox 的摘要說明
/// </summary>
public class SampleTextBox : TextBox, IScriptControl
{
private string _highlightCssClass;
private string _noHighlightCssClass;
private ScriptManager sm;

public string HighlightCssClass
{
get { return _highlightCssClass; }
set { _highlightCssClass = value; }
}

public string NoHighlightCssClass
{
get { return _noHighlightCssClass; }
set { _noHighlightCssClass = value; }
}

protected override void OnPreRender(EventArgs e)
{
if (!this.DesignMode)
{
// Test for ScriptManager and register if it exists
sm = ScriptManager.GetCurrent(Page);

if (sm == null)
throw new HttpException("A ScriptManager control must exist on the current page.");

sm.RegisterScriptControl(this);
}

base.OnPreRender(e);
}

protected override void Render(HtmlTextWriter writer)
{
if (!this.DesignMode)
sm.RegisterScriptDescriptors(this);

base.Render(writer);
}

protected virtual IEnumerable<ScriptReference> GetScriptReferences()
{
ScriptReference reference = new ScriptReference();
reference.Path = ResolveClientUrl("SampleTextBox.js");

return new ScriptReference[] { reference };
}

protected virtual IEnumerable<ScriptDescriptor> GetScriptDescriptors()
{
ScriptControlDescriptor descriptor = new ScriptControlDescriptor("Samples.SampleTextBox", this.ClientID);
descriptor.AddProperty("highlightCssClass", this.HighlightCssClass);
descriptor.AddProperty("nohighlightCssClass", this.NoHighlightCssClass);

return new ScriptDescriptor[] { descriptor };
}

IEnumerable<ScriptReference> IScriptControl.GetScriptReferences()
{
return GetScriptReferences();
}

IEnumerable<ScriptDescriptor> IScriptControl.GetScriptDescriptors()