how to avoid to insert same data into database using C#

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There is one database name as "email_book" and in that database there is one table named as "contact_book"....name and mail_id are the two column which i had been created in that table.......now i want to add data into to my table using form in C# but on the counter part i just want to avoid inserting the repeated data into the table.......when user add same mail_id which is already present in the table then it must gives the message that "this mail_address is already present in database"........so for that i need coading in C#

.....please help its urgent

Posted 12-Feb-14 20:56pm

Gaurav Manusmare

Updated 12-Feb-14 21:22pm

Vedat Ozan Oner

v2

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Solution 2

set mail_id column as IDENTITY. that prevents duplicated key usage.

http://msdn.microsoft.com/en-us/library/ms186775.aspx[^]

Posted 12-Feb-14 21:27pm

Vedat Ozan Oner

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Jignesh Khant · Accepted Answer · 2014-02-12T21:23:00

You can count the value of data that is being inserted like this:

string constr = ConfigurationManager.ConnectionStrings["connstr"].ToString();
        SqlConnection con = new SqlConnection(constr);
        string sql1 = "SELECT COUNT (client_id) FROM client WHERE client_id = '" + txtid.Text + "' ";
        SqlCommand cmd = new SqlCommand(sql1, con);
        con.Open();
        int temp = Convert.ToInt32(cmd.ExecuteScalar().ToString());
       if (temp >0)
        {
//show error message
        }