Stop Inserting 2 Same Words In One Database Field

See my code below... it nicely insert in database data...



but I wish: if user of program in field "txtPozicija" try insert in
database same data detail like is in "Pozicija" field in database that
he be stopped and informed by message: you can not insert TWO SAME data
in the "Pozicija" table.



any advice here?






I AM TRY SOLVE THIS LIKE BELOW, NO ERROR BUT NOT WORK


using System;

using System.Data;

using System.Configuration;

using System.Collections;

using System.Web;

using System.Web.Security;

using System.Web.UI;

using System.Web.UI.WebControls;

using System.Web.UI.WebControls.WebParts;

using System.Web.UI.HtmlControls;

using System.Data.SqlClient;



public partial class adminpanel_Default : System.Web.UI.Page

{

    protected void Page_Load(object sender, EventArgs e)

    {

        lblHR.Text = txtPozicija.Text;

        lblEN.Text = txtLinkZaViseoMjestu.Text;

        lblIT.Text = ddRegija.Text;



    }



    // On dropbox in the html added OnDataBound="MyDataBound" Occurs after the server control binds to a data source.



    protected void myDataBound(Object sender, EventArgs e)

    {

        ddRegija.Items.Insert(0, "--- Selektiraj ---");

    }





    void SaveDataDB()

    {

        string ConnStr = ConfigurationManager.ConnectionStrings["croestate_dbConnectionString"].ConnectionString;

        SqlConnection Conn = new SqlConnection(ConnStr);



        try

        {

            Conn.Open();





            String sqlQuery = "INSERT INTO PozicijaObjekta VALUES(@Pozicija, @LinkzaViseoMjestu, @Regija)";

            SqlCommand cmd = new SqlCommand(sqlQuery, Conn);

            cmd.Parameters.AddWithValue("@Pozicija", txtPozicija.Text);

            cmd.Parameters.AddWithValue("@LinkzaViseoMjestu", txtLinkZaViseoMjestu.Text);

            cmd.Parameters.AddWithValue("@Regija", ddRegija.SelectedValue);



            cmd.ExecuteNonQuery();

        }

        catch (Exception ex)

        {

            Conn.Close();

            Response.Write(ex.Message);

            Wizard1.ActiveStepIndex = 0;

        }



    }

   

   

   



    protected void Wizard1_NextButtonClick(object sender, WizardNavigationEventArgs e)

    {

        if (e.CurrentStepIndex == 0)

        {

            SaveDataDB();

        }



        if (e.CurrentStepIndex == 1)

        {

            //Register user into the database not hear because wizard have one step only

            // SaveDataDB();

        }

    }

    protected void CustomValidator1_ServerValidate(object source, ServerValidateEventArgs args)

    {

        if (ddRegija.SelectedIndex == 0)

            args.IsValid = false;

    }

    protected void CustomValidatorPozicija_ServerValidate(object source, ServerValidateEventArgs args)

    {

        string ConnStr = ConfigurationManager.ConnectionStrings["croestate_dbConnectionString"].ConnectionString;

        SqlConnection Conn = new SqlConnection(ConnStr);



        try

        {

            Conn.Open();





            String sqlQuery = "SELECT Pozicija FROM PozicijaObjekta WHERE Pozicija='" + txtPozicija.TemplateControl + "'";

            SqlCommand cmd = new SqlCommand(sqlQuery, Conn);

            SqlDataReader dr = cmd.ExecuteReader();

            if (dr.Read() == true)

                args.IsValid = false;



        }

        catch (Exception ex)

        {

            Conn.Close();

            Response.Write(ex.Message);

            Wizard1.ActiveStepIndex = 0;

        }

    }

}