Why this mention appear(...)

Hi!
Can I have a solution on this bug. When I run my program I receive this message and I don't see what's wrong because I put the same code as declared in .aspx file: "cmdNew_Click". But I have this message:
1. The type 'AuthorManager' already contains a definition for 'cmdNew_Click'

.aspx
...
ID="cmdNew_Click" text="Create New" runat="server"/>
...

...
protected void cmdNew_Click(object sender, EventArgs e)
{
     txtID.Text="";
     txtFirstName.Text="";
}
...

Then how can resolv it please.

Thanx,
Israel.