The answer to this question has been given inside the comments section, but I would like to add a few more things to that.
What problem was, that your JavaScript was expecting a string-like data to work on, but you were passing a token; variable-like. Which would have been logged as undefined in your console if you would have a look at it.
The solution to it, is to use
''
inside your double quotes; to convert the concatenated data as a string.
ScriptManager.RegisterClientScriptBlock(this, this.GetType(),
"msg", "ShowSubscribe('" + strUrl +"')", true);
There is
another tip[
^] that I have posted for similar conditions, where you miss these concatenations and other such minor mistakes and keep scratching your head to notice where you missed it. String concatenations always cause problems, either pass parameters to
String.Format()[
^], or you should use
StringBuilder[
^] where you are going to use a lot of concatenations.