Error: The request filtering module is configured to deny a request that contains a double escape sequence in ASP.Net

hi

in default.aspx page I put textbox and button that users type text into textbox and when click on button it will redirect to search page below is code:

  protected void Imgsearch_Click(object sender, ImageClickEventArgs e)
    {
        Response.Redirect("Search/" + Server.UrlEncode(TxtsearchI.Text));
    }

but when it redirect search.aspx page below error happen:

and url address is:

http://localhost:61221/Search/water+fall

best regards

neda