OK so I'm trying to improve my asp data entry page to ensure that the entry going into my data table is unique.

So in this table I have SoftwareName and SoftwareType. I'm trying to get it so if the entry page sends an insert query with parameters that match whats in the table (so same title and type) then an error is thrown up and the Data isn't entered.

Something like this:

```
INSERT INTO tblSoftwareTitles( 
            SoftwareName,  
            SoftwareSystemType) 
            VALUES(@SoftwareName,@SoftwareType) 
            WHERE NOT EXISTS (SELECT SoftwareName 
            FROM tblSoftwareTitles 
            WHERE Softwarename = @SoftwareName 
            AND SoftwareType = @Softwaretype)

```

So this syntax works great for selecting columns from one table into another without duplicates being entered but doesn't seem to want to work with a parametrized insert query. Can anyone help me out with this?

Edit:

Here's the code I'm using in my ASP insert method

```
    private void ExecuteInsert(string name, string type)
{
    //Creates a new connection using the HWM string
    using (SqlConnection HWM = new SqlConnection(GetConnectionStringHWM()))
    {
        //Creates a sql string with parameters
        string sql = " INSERT INTO tblSoftwareTitles( "
                   + " SoftwareName, " 
                   + " SoftwareSystemType) "
                   + " SELECT "
                   + " @SoftwareName, "
                   + " @SoftwareType "
                   + " WHERE   NOT EXISTS  "
                   + " ( SELECT  1 "
                   + " FROM tblSoftwareTitles "
                   + " WHERE Softwarename = @SoftwareName "
                   + " AND SoftwareSystemType = @Softwaretype); ";         

        //Opens the connection
        HWM.Open();
        try
        {
            //Creates a Sql command
            using (SqlCommand addSoftware = new SqlCommand{
                CommandType = CommandType.Text,
                Connection = HWM,
                CommandTimeout = 300,
                CommandText = sql})
            {
                //adds parameters to the Sql command
                addSoftware.Parameters.Add("@SoftwareName", SqlDbType.NVarChar, 200).Value = name;
                addSoftware.Parameters.Add("@SoftwareType", SqlDbType.Int).Value = type;
                //Executes the Sql
                addSoftware.ExecuteNonQuery();
            }
            Alert.Show("Software title saved!");
        }
        catch (System.Data.SqlClient.SqlException ex)
        {
            string msg = "Insert Error:";
            msg += ex.Message;
            throw new Exception(msg);
        }

    }
}

```