Passing arguments to JavaScript function from code-behind

Question

I would like to call a javascript function from an aspx control   For instance  suppose I had    lt html xmlns  http   www w3 org 1999 xhtml  gt       lt head runat  server  gt   lt title gt Untitled Page lt  title gt   lt script type  text javascript  gt      function test x  y                lt  script gt   lt  head gt   lt body gt       lt form id  form1  runat  server  gt       lt div gt           lt asp Button ID  Button1  runat  server  Text  Button           onclick  Button1 Click   gt       lt  div gt       lt  form gt   lt  body gt   lt  html gt    and in the code behind   protected void Button1 Click object sender  EventArgs e           do stuff  really going to a database to fill x and y      int   x   new int     1  2  3  4  5        int   y   new int     1  2  3  4  5            call javascript function as test x y       Is there a way to do it

User · Accepted Answer

You can use the Page ClientScript RegisterStartupScript method

User · Answer

lt head gt       lt script type  text javascript  gt           function test x  y                         var cc                   for  var i   0  i  lt  x length  i                                   cc    x i                              cc      ny      y               return cc                  lt  script gt      lt  head gt    lt body gt        lt form id  form1  runat  server  gt            lt asp Button ID  Button1  runat  server  Text  Button      gt            lt p gt                lt asp TextBox ID  TextBox1   Name  TextBox1   runat  server  AutoPostBack  True   TextMode  MultiLine  gt  lt  asp TextBox gt           lt  p gt          lt  form gt   lt  body gt   protected void Page Load object sender  EventArgs e        int   x   new int     1  2  3  4  5        int   y   new int     1  2  3  4  5         string xStr   getArrayString x      converts  1 2 3 4 5  to  1 2 3 4 5      string yStr   getArrayString y        string script   String Format   var y   test  0   1        xStr  yStr       script    String Format    document getElementById   TextBox1    value   y           this Page ClientScript RegisterStartupScript this GetType      testFunction   script  true         this Page ClientScript RegisterClientScriptBlock this GetType     testFunction   script  true      different result       private string getArrayString int   array        StringBuilder sb   new StringBuilder        for  int i   0  i  lt  array Length  i                  sb Append array i                    string arrayStr   string Format    0     sb ToString   TrimEnd            return arrayStr

User · Answer

I think you want to execute the javascript serverside and not in the browser after post-back  right   That s not possible as far as I know  If you just want to get it execute after postback  you can do something like this   this Page ClientScript RegisterClientScriptBlock this GetType     xx     lt script gt test   x     y     lt  script gt

User · Answer

Some other things I found out   You can t directly pass in an array like   this Page ClientScript RegisterClientScriptBlock this GetType     xx        lt script gt test   x     y     lt  script gt       because that calls the ToString   methods of x and y  which returns  System Int32     and obviously Javascript can t use that   I had to pass in the arrays as strings  like   1 2 3 4 5    so I wrote a helper method to do the conversion   Also  there is a difference between this Page ClientScript RegisterStartupScript   and this Page ClientScript RegisterClientScriptBlock   - the former places the script at the bottom of the page  which I need in order to be able to access the controls  like with document getElementByID    RegisterClientScriptBlock   is executed before the tags are rendered  so I actually get a Javascript error if I use that method   http   www wrox com WileyCDA Section Manipulating-ASP-NET-Pages-and-Server-Controls-with-JavaScript id-310803 html covers the difference between the two pretty well   Here s the complete example I came up with      code behind protected void Button1 Click object sender  EventArgs e        int   x   new int     1  2  3  4  5        int   y   new int     1  2  3  4  5         string xStr   getArrayString x      converts  1 2 3 4 5  to  1 2 3 4 5      string yStr   getArrayString y        string script   String Format  test  0   1     xStr  yStr       this Page ClientScript RegisterStartupScript this GetType         testFunction   script  true         this Page ClientScript RegisterClientScriptBlock this GetType           testFunction   script  true      different result   private string getArrayString int   array        StringBuilder sb   new StringBuilder        for  int i   0  i  lt  array Length  i                  sb Append array i                    string arrayStr   string Format    0     sb ToString   TrimEnd            return arrayStr       aspx page  lt html xmlns  http   www w3 org 1999 xhtml  gt   lt head runat  server  gt       lt title gt Untitled Page lt  title gt       lt script type  text javascript  gt      function test x  y                var text1   document getElementById  text1           for var i   0  i lt x length  i                          text1 innerText    x i      prints 12345                   text1 innerText      ny      y     prints y  1 2 3 4 5              lt  script gt   lt  head gt   lt body gt       lt form id  form1  runat  server  gt       lt div gt           lt asp Button ID  Button1  runat  server  Text  Button           onclick  Button1 Click    gt       lt  div gt       lt div id   text1  gt        lt  div gt       lt  form gt   lt  body gt   lt  html gt

User · Answer

Response Write   lt scrip     t gt test     x         y       lt  script gt       breaking up the script keyword because VStudio   asp net compiler doesn t like it

User · Answer

Look at the ScriptManager RegisterStartupScript method if you re using a ScriptManager or any Ajax controls asynchronous postbacks   Edit   Actually  the function you want is probably ScriptManager RegisterClientScriptBlock

User · Answer

include script manager  code behind function  ScriptManager RegisterStartupScript this  this GetType     HideConfirmBox    javascript HideAAConfirmBox       true

User · Answer

If you are interested in processing Javascript on the server  there is a new open source library called Jint that allows you to execute server side Javascript   Basically it is a Javascript interpreter written in C    I have been testing it and so far it looks quite promising  Here s the description from the site   Differences with other script engines  Jint is different as it doesn t use CodeDomProvider technique which is using compilation under the hood and thus leads to memory leaks as the compiled assemblies can t be unloaded  Moreover  using this technique prevents using dynamically types variables the way JavaScript does  allowing more flexibility in your scripts  On the opposite  Jint embeds it s own parsing logic  and really interprets the scripts  Jint uses the famous ANTLR  http   www antlr org  library for this purpose  As it uses Javascript as its language you don t have to learn a new language  it has proven to be very powerful for scripting purposes  and you can use several text editors for syntax checking

User · Answer

lt html xmlns  http   www w3 org 1999 xhtml  gt   lt head runat  server  gt       lt title gt Call java script function on Code behind lt  title gt       lt script  type  text javascript  gt      function abc                 var a 20          var b 30          alert  you enter  a     b              lt  script gt   lt  head gt    cs code  protected void Page Load object sender  EventArgs e        TextBox2 Attributes Add  onkeypress    return abc           try this

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