Call JavaScript function on DropDownList SelectedIndexChanged Event

Question

I have written one JavaScript function as follows    function CalcTotalAmt           ----------     -----------      I have one DropDownList       lt asp DropDownList ID  ddl  runat  server   AutoPostBack  true  OnSelectedIndexChanged  ddl SelectedIndexChanged  gt  lt  asp DropDownList gt    I need to call the above JavaScript function in the DropDownList s SelectedIndexChanged Event  I tried like below   protected void ddl SelectedIndexChanged object sender  EventArgs e        ddl Attributes Add  onchange    return CalcTotalAmt           But the JavaScript function is not executing  How to call the JavaScript function in DropDownList Change Event

User · Answer

Or you can do it like as well    lt asp DropDownList ID  ddl  runat  server   AutoPostBack  true  onchange  javascript CalcTotalAmt     OnSelectedIndexChanged  ddl SelectedIndexChanged  gt  lt  asp DropDownList gt

User · Answer

You can use the ScriptManager RegisterStartupScript    to call any of your javascript event Client Event from the server  For example  to display a message using javascript s alert     you can do this   protected void ddl SelectedIndexChanged object sender  EventArgs e    Response write   lt script gt alert  This is my message    lt  script gt        ----or alternatively and to be more proper  ScriptManager RegisterStartupScript this  this GetType     callJSFunction    alert  This is my message     true       To be exact for you  do this     protected void ddl SelectedIndexChanged object sender  EventArgs e     ScriptManager RegisterStartupScript this  this GetType     callJSFunction    CalcTotalAmt      true

User · Answer

First Method   Tested   Code in  aspx cs    protected void Page Load object sender  EventArgs e                ddl SelectedIndexChanged    new EventHandler ddl SelectedIndexChanged           if   Page IsPostBack                        ddl Attributes Add  onchange    CalcTotalAmt                            protected void ddl SelectedIndexChanged object sender  EventArgs e                 Your Code         JavaScript function  return true from your JS function     function CalcTotalAmt         Your Code       aspx code    lt asp DropDownList ID  ddl  runat  server   AutoPostBack  true  gt           lt asp ListItem Text  a  Value  a  gt  lt  asp ListItem gt            lt asp ListItem Text  b  Value  b  gt  lt  asp ListItem gt           lt  asp DropDownList gt    Second Method   Tested   Code in  aspx cs   protected void Page Load object sender  EventArgs e                        if  Request Params    EVENTARGUMENT      null  amp  amp  Request Params    EVENTARGUMENT   Equals  ddlchange                    ddl SelectedIndexChanged sender  e               if   Page IsPostBack                                ddl Attributes Add  onchange    CalcTotalAmt                                        protected void ddl SelectedIndexChanged object sender  EventArgs e                          Your Code             JavaScript function  return true from your JS function  function CalcTotalAmt                Your Code        doPostBack  ctl00 MainContent ddl   ddlchange          aspx code    lt asp DropDownList ID  ddl  runat  server   AutoPostBack  true  gt           lt asp ListItem Text  a  Value  a  gt  lt  asp ListItem gt            lt asp ListItem Text  b  Value  b  gt  lt  asp ListItem gt           lt  asp DropDownList gt

[javascript] Call JavaScript function on DropDownList SelectedIndexChanged Event:

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