How to pass a string from C# to a javascript variable

Question

i like to pass a string from C# to a javascript variable. The simple way is like:

string aaa = "hello";

and then

<script>
    var javacriptVariable = "<%=aaa%>";
</script>

But, I am asking if there is another way without using a <script> block to to make that variable into a javascript equivalent, direclty using ONLY C# code.

Thank you.

You could use RegisterClientScriptBlock to write the javascript that sets the variable. Or use json to pull the variable. — the_lotus
– the_lotus, Commented Oct 8, 2013 at 17:36
How do you expect to use the javascript var if it's not inside a script block? — Simon
– Simon, Commented Oct 8, 2013 at 17:36
RegisterStartupScript msdn.microsoft.com/en-us/library/bahh2fef.aspx — gp.
– gp., Commented Oct 8, 2013 at 17:40
You could have a HiddenField in your ASP.NET page and you can set it with C# and access it with javascript. — Icemanind
– Icemanind, Commented Oct 8, 2013 at 18:36

ispiro · Accepted Answer · 2013-10-08 18:11:30Z

2

Write it to a div's InnerHtml in C#, and get the div's innerHTML from your JavaScript code.

Notes:

You'll have to make the div runat="server".
Notice the difference in the casing (uppercase/lowercase) between the C#'s InnerHtml and js's innerHTML .

answered Oct 8, 2013 at 18:11

ispiro

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Comments

Brad Christie · Accepted Answer · 2013-10-08 17:41:55Z

Well, the best method would be to include JSON.NET and output it:

var aaa = <%= JsonConvert.Serialize(aaa) %>;

Then, no matter if it's a string, integer, array, or whatever it'll be serialized in a way that JS can handle it. this will also handle any kind of escaping if necessary (e.g. aaa = "Hello \"World\"!")

Another option is to retrieve it with a handler/AJAX (but that's a little too much overhead for such a simple task).

Finally, you can register the script:

Type type = this.GetType();
string scriptName = "assign aaa";
ClientScriptManager clientScript = Page.ClientScript;
if (!clientScript.IsClientScriptBlockRegistered(type, scripName))
{
    StringBuilder sb = new StringBuilder();
    sb.Append("<script type=\"text/javascript\">")
      .AppendFormat("var aaa = {0};", JsonConvert.Serialize(aaa))
      .Append("</" + "script>");
    clientScript.RegisterClientScriptBlock(type, scripName, sb.ToString());
}

But the above is just a more elaborate way of ending up with a <script> tag anyways.

BFree · Accepted Answer · 2013-10-08 17:50:40Z

0

I actually created a nuget pacakge called Ngon that does exactly this:

http://www.nuget.org/packages/NGon/

It's a rip of the rails gem Gon

answered Oct 8, 2013 at 17:50

BFree

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