Question

Possible Duplicate:
The variable name ‘@VarName’ has already been declared Issue

using (SqlCommand command = connection.CreateCommand())
{
    int j = 1;
    for (int i = 0; i < temp4.Count; i++)
    {
        #region idsetter

        int prevId = 0;

        command.CommandText = "SELECT MAX(id) FROM Configuration";
        connection.Open();
        using (SqlDataReader reader = command.ExecuteReader())
        {
            while (reader.Read())
            {
                if (reader[0].ToString() != "")
                {
                    prevId = Int32.Parse(reader[0].ToString());
                }
                else
                {
                    prevId = 0;
                }
            }
        }

        connection.Close();
        int currId = prevId + 1;
        #endregion
        command.CommandText = "INSERT INTO Configuration (id,A, B, C, D, E, F,G) " + 
                              "VALUES (@id, @a, @b , @c, @d, @e, @f, @g)";

        command.Parameters.AddWithValue("@id", currId);
        command.Parameters.AddWithValue("@a", myL);
        command.Parameters.AddWithValue("@b", pipi);
        command.Parameters.AddWithValue("@c", temp4[i].ad);
        command.Parameters.AddWithValue("@d", temp4[i].asa);
        command.Parameters.AddWithValue("@e", temp4[i].Tasa);
        command.Parameters.AddWithValue("@f", j);
        command.Parameters.AddWithValue("@g", 1);
        connection.Open();
        command.ExecuteNonQuery();
        connection.Close();
        j++;
        if (j > 7)
        {
            j = 1;
        }
    }
}

I am trying to write in Configuration Table first reading id and increment it and then writing everything else. But when second entry is being added it gives exception

The variable name “@id” has already been declared. Variable names
must be unique within a query batch or stored procedure.

How to avoid this exception any work around ?

Answer 1

You need to clear your Command parameters in every iteration of your loop.

command.CommandText = "INSERT INTO Configuration (id,A, B, C, D, E, F,G) VALUES (@id, @a, @b , @c, @d, @e, @f, @g)";

command.Parameters.Clear();
command.Parameters.AddWithValue("@id", currId);