判断用户是否存在.txt

学习积累的代码段

string UserName=this.txtname.Text;
			string Uid=this.txtpwd.Text;
			SqlConnection con=DB.creatcon();
			con.Open();
			SqlCommand cmd=new SqlCommand ("select count(*) from users  where UserName='"+UserName+"'and Uid='"+Uid+"'",con);
			int count =Convert.ToInt32(cmd.ExecuteScalar());
			if(count>0)
			{
				Response.Write("<script language='javascript'>alert('该用户已经存在！')</script>");
				Response.Redirect("check.aspx");

				
			}
			else
			{
				Response.Redirect("login.aspx");

				
				
			}