Check username and password is incorrect in asp.net

Question

when user login if username is incorrect then it will show error if password is incorrect its shows error...in my code its is username or password is incorrect then it will show error.. i want for both condition.this all done by Entity Framework

 

protected void Button1_Click(object sender, EventArgs e)

{

string UserName = TxtUserName.Text;

WallpaperEntities4 db = new WallpaperEntities4();

string ID = Request.QueryString["Id"];

string query = (from c in db.Users

where c.UserName == TxtUserName.Text && c.Password == TxtPassword.Text

select c.UserName).FirstOrDefault();

if (query != null)

{

Session["UserName"] = UserName;

Response.Redirect("/Walpaper.aspx?username="+UserName);

}

else

LblMesge.Text = "Invalid User or password";

}