You can try this code:

MyCompany.Web.Utilities.PageUtilityLib.RegisterGenericJavaScriptBlock is
just a wrapper for registering a client side java script.

MyCompany.Web.Utilities.ObjectUtilityLib.AppendAttribute is just a wrapper
for myControl.Attributes.Add( .......... )

You should get the idea.

This handles 3 types of controls.

       private static readonly string HREF_ALREADY_CLICKED_VARIABLE_NAME =
"hrefAlreadyClicked";
       private static readonly string
HREF_ALREADY_CLICKED_VARIABLE_NAME_JS_KEY =
"HREF_ALREADY_CLICKED_VARIABLE_NAME_JS_KEY";

       /// <summary>
       /// Provides the double submit prevention on controls issuing a
PostBack.
       /// </summary>
       /// <param name="TargetPage">The target page.</param>
       /// <param name="c">The control.</param>
       public static void DoubleSubmitPrevention(Page TargetPage,
System.Web.UI.WebControls.WebControl c)
       {
           DoubleSubmitPrevention(TargetPage, c, string.Empty);
       }

       /// <summary>
       /// Doubles the submit prevention.
       /// </summary>
       /// <param name="TargetPage">The target page.</param>
       /// <param name="c">The control which needs double submit
prevention.  Button, LinkButton, or ImageButton.</param>
       /// <param name="submitImageName">Name of the submit image.</param>
       public static void DoubleSubmitPrevention(Page TargetPage,
System.Web.UI.WebControls.WebControl c, string submitImageName)
       {
           DoubleSubmitPrevention(TargetPage, c, submitImageName, 125);// a
125 milliseconds delay seems to be a good balance
       }

       /// <summary>
       /// Provides the double submit prevention on controls issuing a
PostBack.
       /// </summary>
       /// <param name="TargetPage">The target page.</param>
       /// <param name="c">The control which needs double submit
prevention.  Button, LinkButton, or ImageButton.</param>
       /// <param name="submitImageName">Name of the alternate image to
show while the PostBack is occuring.</param>
       /// <param name="imageDelayMilliseconds">The image delay
milliseconds.  Suggested value is around 125.</param>
       public static void DoubleSubmitPrevention(Page TargetPage,
System.Web.UI.WebControls.WebControl c, string submitImageName, int
imageDelayMilliseconds)
       {

           string wcUID = c.ID;

           // We need a member variable to track this.......so register it
here
           MyCompany.Web.Utilities.PageUtilityLib.RegisterGenericJavaScriptBlock(TargetPage,
"var " + HREF_ALREADY_CLICKED_VARIABLE_NAME + "=false;",
HREF_ALREADY_CLICKED_VARIABLE_NAME_JS_KEY, true);

           string pleaseWait = "Please Wait...";

           System.Text.StringBuilder sb = new System.Text.StringBuilder();
           if (TargetPage.Validators.Count > 0)
           {
               sb.Append("if (typeof(Page_ClientValidate) == 'function')
{ ");
               sb.Append("if (Page_ClientValidate() == false) { return
false; }} ");
           }
           if ((c is System.Web.UI.WebControls.Button))
           {
               sb.Append("this.value = '" + pleaseWait + "';");
           }
           else if ((c is System.Web.UI.WebControls.LinkButton))
           {
               sb.Append("this.innerHTML = '" + pleaseWait +
"';if(hrefAlreadyClicked==false){" + HREF_ALREADY_CLICKED_VARIABLE_NAME +
"=true;return true;}else{this.innerHTML+='...';return false;};");
           }
           else if ((c is System.Web.UI.WebControls.ImageButton))
           {
               MyCompany.Web.Utilities.PageUtilityLib.RegisterGenericJavaScriptBlock(TargetPage,
"var imgSaveButtonAlternate = new Image().src = '" + submitImageName + "'",
"ImagePreLoad", true);
               sb.Append("this.src = '" + submitImageName + "';");
               sb.Append("setTimeout('" +
TargetPage.ClientScript.GetPostBackEventReference(c , null).Replace("'",
"\\'") + ";', " + imageDelayMilliseconds + ");");
           }
           else
           {
               throw new ArgumentException("This procedure only accepts '
System.Web.UI.WebControls.Button', 'System.Web.UI.WebControls.LinkButton' ,
and ' System.Web.UI.WebControls.ImageButton' objects");
           }

           sb.Append("this.disabled=true;");

           if (!((c is System.Web.UI.WebControls.ImageButton)))
           {
               sb.Append(TargetPage.ClientScript.GetPostBackEventReference(c,
null));
           }
           sb.Append(";");
           MyCompany.Web.Utilities.ObjectUtilityLib.AppendAttribute(c,
"onClick", sb.ToString(), Web.Utilities.AppendOrder.AFTER_CURRENT_ITEMS);
           sb = null;
       }

<asp:Button ID="cmdSubmit" runat="server" Text="Submit"
OnClick="cmdSubmit_Click" OnClientClick="this.disabled=true;" />