asp.net javascript message not showing up
Question
I have a button and onclick is set to this method which should display a simple JS alert pop up window:
string message = "File is already open. <br>Please close the file and try again.";
System.Text.StringBuilder sb = new System.Text.StringBuilder();
sb.Append("<script type = 'text/javascript'>");
sb.Append("window.onload=function(){");
sb.Append("alert('");
sb.Append(message);
sb.Append("')};");
sb.Append("</script>");
ClientScript.RegisterClientScriptBlock(this.GetType(), "alert", sb.ToString());
I have used the code above before and it has worked but not this time. The only difference is that I was using master pages for the other site and not for this one, and this one also has a timer going.
Is there anything JS related to load in the <head> of the aspx page?
protected void btnToCSV_Click(object sender, EventArgs e)
{
try
{
StreamWriter writer = new StreamWriter(@"\\server location\test.csv");
Some writer.write stuff...
writer.Close();
}
catch (Exception ex)
{
lblMessage.Visible = true;
string message = "File is already open. Please close the file and try again.";
ClientScript.RegisterClientScriptBlock(
this.GetType(),
"alert",
string.Format("alert('{0}');", message),
true);
}
}
2 answers
solution1
3 ACCPTED 2012-06-29 17:40:18
Try with this simplyfied version
string message = "File is already open. <br>Please close the file and try again.";
ScriptManager.RegisterClientScriptBlock(
UpdatePanel1, // replace UpdatePanel1 by your UpdatePanel id
UpdatePanel1.GetType(), // replace UpdatePanel1 by your UpdatePanel id
"alert",
string.Format("alert('{0}');",message),
true );
solution2
2 2012-06-29 17:39:47
You are not encoding anything here:
sb.Append(message);
If the message is Hello Jean d'Arc (notice the single quote) you will end up with the following code:
alert('Hello Jean d'Arc');
I am leaving you imagine the result of this => a javascript error of course.
To fix this error make sure that you have properly encoded the argument. One way to do this is to JSON serialize it:
var serializer = new JavaScriptSerializer();
sb.AppendFormat("alert({0});", serializer.Serialize(message));
Also since you have already includeed the <script> tags, make sure that you pass false as last argument of the RegisterClientScriptBlock function to avoid adding them twice:
ClientScript.RegisterClientScriptBlock(
this.GetType(),
"alert",
sb.ToString(),
false // <!---- HERE
);
And here's how the full code might look like:
var message = "File is already open. <br>Please close the file and try again.";
var sb = new StringBuilder();
sb.Append("<script type=\"text/javascript\">");
sb.Append("window.onload=function() {");
var serializer = new JavaScriptSerializer();
sb.AppendFormat("alert({0});", serializer.Serialize(message));
sb.Append("};");
sb.Append("</script>");
ClientScript.RegisterClientScriptBlock(
this.GetType(),
"alert",
sb.ToString(),
false
);
Another remark is that if you are doing this in an AJAX call you should use the ClientScript.RegisterStartupScript method.
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