How to use doPostBack

Question

I m trying to create an asyncrhonous postback in ASP NET using   doPostBack    but I have no idea how to do it   I want to use vanilla JavaScript   Something simple like a button click can cause the   doPostBack   event to fire   I m just trying to learn how the mechanism works

User · Answer

This is also a good way to get server-side controls to postback inside FancyBox and/or jQuery Dialog. For example, in FancyBox-div:

   <asp:Button OnClientClick="testMe('param1');" ClientIDMode="Static"  ID="MyButton"  runat="server" Text="Ok" >
</asp:Button>

JavaScript:

function testMe(params) {
    var btnID= '<%=MyButton.ClientID %>';          
    __doPostBack(btnID, params);
}

Server-side Page_Load:

 string parameter = Request["__EVENTARGUMENT"];
 if (parameter == "param1")
     MyButton_Click(sender, e);

User · Answer

This is how I do it      public void B ODOC OnClick Object sender  EventArgs e                string script   lt script gt   doPostBack   fileView ctl01 OTHDOC        EventArgument     OpenModal     EncryptedData   null      lt  script gt            Page ClientScript RegisterStartupScript this GetType    JsOtherDocuments  script

User · Answer

You can try this in your web form with a button called btnSave for example    lt input type  button  id  btnSave  onclick  javascript SaveWithParameter  Hello Michael    value  click me   gt    lt script type  text javascript  gt  function SaveWithParameter parameter        doPostBack  btnSave   parameter     lt  script gt    And in your code behind add something like this to read the value and operate upon it   public void Page Load object sender  EventArgs e      string parameter   Request    EVENTARGUMENT       parameter      Request    EVENTTARGET       btnSave     Give that a try and let us know if that worked for you

User · Answer

Like others have said  you need to provide the UniqueID of the control to the   doPostback   method      doPostBack   lt    btn UniqueID   gt           On the server  the submitted form values are identified by the name attribute of the fields in the page    The reason why UniqueID works is because UniqueID and name are in fact the same thing when the server control is rendered in HTML   Here s an article that describes what is the UniqueID       The UniqueID property is also used to provide value for the HTML    name  attribute of input fields  checkboxes  dropdown lists  and   hidden fields   UniqueID also plays major role in postbacks  The   UniqueID property of a server control  which supports postbacks    provides data for the   EVENTTARGET hidden field  The ASP NET Runtime   then uses the   EVENTTARGET field to find the control which triggered   the postback and then calls its RaisePostBackEvent method       src    https   www telerik com blogs the-difference-between-id-clientid-and-uniqueid

User · Answer

Old question  but I d like to add something  when calling doPostBack   you can use the server handler method for the action   For an example     doPostBack   lt    btn UniqueID  gt     my args      Will fire  on server   protected void btn Click object sender  EventArgs e    I didn t find a better way to get the argument  so I m still using Request    EVENTARGUMENT

User · Answer

I d just like to add something to this post for asp button  I ve tried clientId and it doesn t seem to work for me     doPostBack   lt    btn ClientID  gt           However  getting the UniqueId seems to post back to the server  like below     doPostBack   lt    btn UniqueID  gt           This might help someone else in future  hence posting this

User · Answer

Here s a brief tutorial on how   doPostBack   works   To be honest  I don t use it much  at least directly  Many server controls   e g   Button  LinkButton  ImageButton  parts of the GridView  etc   use   doPostBack as their post back mechanism

[c#] How to use __doPostBack()

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