Some Useful Stuff in Dot Net

1. How to check UserId available in database or not ?

A : First design the page like 

Source Page, 

Code behind, 

 protected void Button1_Click(object sender, EventArgs e)

        {

            SqlConnection con = new SqlConnection(str);

            con.Open();

            SqlCommand cmd = new SqlCommand("select count(*) from test where testid=" + TextBox1.Text.Trim(), con);

            int i = Convert.ToInt32(cmd.ExecuteScalar());

            if (i > 0)

            {

                Label3.Text = "This UserId is already existed";

            }

            else

            {

                Label3.Text = "This User Id not existed";

            }

        }

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2. How to find the last 2 characters in a given input string 

Code behind,

string str=txtinput.Text.Trim().Substring(Math.Max(0,txtinput.Text.Trim().Length-2));

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