Bookcold's Blog » JavaScript http://bookcold.com Just for pleasure Sun, 29 Aug 2010 06:39:14 +0000 en hourly 1 JavaScript与后台代码交互 http://bookcold.com/2010/01/218 http://bookcold.com/2010/01/218#comments Sun, 10 Jan 2010 05:09:28 +0000 bookcold http://bookcold.com/2010/01/10/218/

Calling & Writing JavaScript Function from Server Side Code Behind

   1:  private void Page_Load(object sender, System.EventArgs e)
   2:  {
   3:      string jScriptValidator;
   4:      jScriptValidator="<script> function ReqFieldValidator()" +
   5:                  " { if (document.forms[0].txtField.value == '') \n";
   6:      jScriptValidator+="{ alert('TextBox cannot be empty') \n ";
   7:      jScriptValidator+="return false; \n";
   8:      jScriptValidator+="} \n";
   9:      jScriptValidator+=" return true \n";
  10:      jScriptValidator+=" } </script>";
  11:      Page.RegisterStartupScript("regJSval",jScriptValidator);
  12:      btnSubmit.Attributes.Add("onclick","return ReqFieldValidator()");
  13:  }

Writing JavaScript Function in Server Side Code Behind and Calling from HTML

   1:  private void Page_Load(object sender, System.EventArgs e)
   2:  {
   3:      string jScript;
   4:      jScript="<script>function JavScriptFn(){alert" +
   5:        " ('Client Function in javascript is call')}</script>";
   6:  }

    1:  //HTML side

   2:  < A onclick="JavScriptFn()" >
   3:  < asp:Label id="Label1" runat="server" Width="281px"
   4:     ForeColor="#8080FF">Click to call Javascript function.
   5:  </asp:Label> >/A >

Writing JavaScript in HTML and Calling it from Code-behind

   1:   <Head >
   2:          <script>
   3:  
   4:          function ReqField1Validator()
   5:          {
   6:           if (document.forms[0].txtField1.value == '')
   7:              {
   8:                  alert('TextBox cannot be empty')
   9:                  return false
  10:              }
  11:                  return true
  12:          }
  13:  
  14:          </script>
  15:  </Head >
   1:  private void Page_Load(object sender, System.EventArgs e)
   2:  {
   3:      btnOK.Attributes.Add("onclick","return ReqField1Validator()");
   4:  }

RegisterClientScriptBlock

   1:  private void btnClientBlock_Click(object sender, System.EventArgs e)
   2:  {
   3:      string jScript;
   4:      jScript="<script>alert ('Javascript block of code executed')</script>";
   5:      Page.RegisterClientScriptBlock("keyClientBlock",jScript);
   6:      lblSequencial.Text="Remaining part of the code executed";
   7:  }

ASP.NET 2.0 RegisterClientScriptBlock/RegisterStartupScript

   1:  <script>
   2:      function fnShowMessage()
   3:      {
   4:          alert(" Invoke Javascript function from Server Side Code Behind ");
   5:      }
   6:  </script>

   1:  protected void Button1_Click(object sender, EventArgs e)
   2:  {
   3:          ClientScript.RegisterStartupScript
   4:          (GetType(),"Javascript", "javascript: fnShowMessage(); ",true);
   5:  }
   6:      protected void Button2_Click(object sender, EventArgs e)
   7:  {
   8:          ClientScript.RegisterClientScriptBlock(GetType(), "Javascript",
   9:          "<script>alert('Record Added Successfully')</script>");
  10:  }

转载自：http://www.codeproject.com/KB/aspnet/ClientServer.aspx

]]> http://bookcold.com/2010/01/218/feed 0 How to call Postback from Javascript （JS带参数调用后台函数） http://bookcold.com/2009/12/166 http://bookcold.com/2009/12/166#comments Fri, 18 Dec 2009 12:13:35 +0000 bookcold http://bookcold.com/2009/12/how-to-call-postback-from-javascript-%ef%bc%88js%e5%b8%a6%e5%8f%82%e6%95%b0%e8%b0%83%e7%94%a8%e5%90%8e%e5%8f%b0%e5%87%bd%e6%95%b0%ef%bc%89/ Postback is a concept introduced in ASP.NET and is a very handy method. Postback is built into the ASP.NET and most of the web controls support it without writing any code. Calling postback event from Javascript

There may be some scenario where you may want to explicitly postback to the server using some [...]]]> Introduction

Postback is a concept introduced in ASP.NET and is a very handy method. Postback is built into the ASP.NET and most of the web controls support it without writing any code.

Calling postback event from Javascript

There may be some scenario where you may want to explicitly postback to the server using some clientside javascript. It is pretty simple to do this.
ASP.NET already creates a client side javascript method as shown below to support Postbacks for the web controls: 

function __doPostBack(eventTarget, eventArgument) {
    if (!theForm.onsubmit || (theForm.onsubmit() != false)) {
        theForm.__EVENTTARGET.value = eventTarget;
        theForm.__EVENTARGUMENT.value = eventArgument;
        theForm.submit();
    }
}

So, all you have to do is, just call this method with appropriate arguments. You may call this as shown below: 

<script language='Javascript'>
__doPostBack('__Page', 'MyCustomArgument');
</script>

However, it is not recommended to use this method name directly in the client side. The best approach is, generate this piece of code from the code behind file using ASP.NET. This way, you are safe even if Microsoft later change the name of the method ‘__doPostBack’ to something else in a future release.

In your code behind file, declare a protected variable as shown below:

Protected PostBackStr As String

Now, in the page load event, write the following code:

PostBackStr = Page.ClientScript.GetPostBackEventReference(Me, "MyCustomArgument")

The method GetPostBackEventReference() will generate the same piece of client side code that you need to use to call the Postback method. Instead of harcoding the method name __doPostBack, we are asking ASP.NET to tell us what is the method name.

Now insert the following code in your Aspx page:

<script language='Javascript'>
<%= PostBackStr %>
</script>

At runtime, it will be evaluated as:

<script language='Javascript'>
__doPostBack('__Page', 'MyCustomArgument');
</script>

Remember to insert the above script into some Javascript method/event where you want to call the postback, instead of simply inserting into the page as shown above.

How to identify and handle the postback in code behind ?

You found how to call the postback from javascript. Now you need a way to identify your postback in the code behind file. The second argument the doPostback method becomes helpful here.

Go to the code behind file and write the following code in the Page Load event:

If Page.IsPostBack Then
   Dim eventArg As String = Request("__EVENTARGUMENT")
   If eventArg = "MyCustomArgument" Then
       Response.Write("You got it !")
   End If
End If

Did you notice how we identify if the page is loaded as part of our postback? We used the second argument in the __doPostBack method to pass a value and used that in PageLoad to identify if it is called as a result of our PostBack.

转载自：http://www.dotnetspider.com/resources/1521-How-call-Postback-from-Javascript.aspx

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