[求助]数据库连接问题（菜鸟学做BBS）

<script language="C#" runat="server">
void Button1_Click(object sender, System.EventArgs e)
{
if (Page.IsValid)
{
if (UserValid())
{
SqlConnection conn = new SqlConnection("server=(local);database=bbs;uid=sa;Pwd=ggj840507");
string sql = "Insert into Users(UserName,Password,Email) values('" +
this.TextBox1.Text + "','" + this.TextBox2.Text + "','" + this.TextBox4.Text + " ')";
SqlCommand cmd = new SqlCommand(sql, conn);
try
{
cmd.ExecuteNonQuery();
}
catch
{
}
finally
{
cmd.Dispose();
conn.Close();
}
this.Panel1.Visible = false;
}
else
{
this.Label1.Visible = false;
}
}
}

private bool UserValid()
{
SqlConnection conn = new SqlConnection("server=(local);database=bbs;uid=sa;Pwd=ggj840507");
string sql = "select * from Users where UserName='" + this.TextBox1.Text + "'";
SqlCommand cmd = new SqlCommand(sql, conn);
SqlDataReader reader = cmd.ExecuteReader();
if (reader.Read())
{
return false;
}
else
{
return true;
}
}
</script>

楼上的那位MM，你看嘛，我有那句打开数据连接话，问题还是依旧。。。。。。。。