Error: An Item With The Same Key Has Already Been Added.

hello.

can you put a small demo page tha reproduces this problem?

Well, I figured what was causing the problem, but not the problem itself.

If I remove this line from my Page Load it works fine:

ClientScript.RegisterHiddenField("__EVENTTARGET", "btnSubmit")

Any ideas? Does ajax consider "_" to be an invalid character?

Thanks again.

According tothis thread, you might want to try:

ScriptManager.RegisterHiddenField(myUpdatePanel,"__EVENTTARGET", "btnSubmit");

hello again.

can't you put a simple page with2 or 3 buttons + the code that reproduces this problem? I'm still not convinced about the cause of therror being that event registration.

Well, I'm a little frustrated because the sample sites I put together both worked (including the above code). I'm not sure what else I'm missing. All I know is that on my production site - this works:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
txtUserID.Focus()
Status.Text = ""
Visibility(False)
End Sub

And this doesn't:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
ClientScript.RegisterHiddenField("__EVENTTARGET", "btnSubmit")
txtUserID.Focus()
Status.Text = ""
Visibility(False)
End Sub

Anyone see anything obvious?

Did you try the my suggestion?
No. The purpose of the code was to set the default "enter key" button to btnSubmit. I ended up using the defaultbutton property of a panel, however, I never knew about scriptmanager.registerhiddenfield - so your suggestion was helpful. Thank you!

Hi celldss,

I was having this problem too, and this thread helped me by showing me where the problem was:

ScriptManager.RegisterHiddenField() or ClientScript.RegisterHiddenField() orPage.RegisterHiddenField()

I think the solution will have you kicking yourself -

I found that it worked for me if I called the RegisterHiddenField() only on the first page load, and not on subsequent postbacks! I guess it tries to register the same field on each postback otherwise. So my code is:

 
protected void Page_Load(object sender, EventArgs e) {if (!this.IsPostBack) { ScriptManager.RegisterHiddenField(this.updatePanel,"__EVENTTARGET","ButtonName"); } }
 
I hope this works for you!