Access DB数据类型不匹配

Question

I keep getting a 'data type mismatch in criteria expression' when trying to insert into my Access 2010 table. The table has field names of: GradeKey - AutoNumber, Grade - Text, Comments - Text, TellerNum - Number, TestName - Text. The TestName is also a foreign key from another table. Any ideas on what I need to use to fix the data type mismatch?

using (OleDbConnection con = new OleDbConnection(constring))
        {
            try
            {

                string cmdstring = "INSERT INTO GRADE (Grade, Comments, TellerNum, TestName) VALUES (@grade, @comments, @teller, @test)";
                using (OleDbCommand cmd = new OleDbCommand(cmdstring, con))
                {
                    cmd.Parameters.AddWithValue("@teller", OleDbType.Integer).Value = comboBox5.Text;
                    cmd.Parameters.AddWithValue("@grade", OleDbType.Char).Value = textBox7.Text;
                    cmd.Parameters.AddWithValue("@comments", OleDbType.Char).Value = textBox10.Text;
                    cmd.Parameters.AddWithValue("@test", OleDbType.Char).Value = comboBox16.Text;

                    con.Open();
                    cmd.ExecuteNonQuery();
                    con.Close();
                    MessageBox.Show("Submitted Successfully");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Failed due to " + ex.Message);
            }
        }

Answer 1

OleDbType.Integer应该是一个整数， OleDbType.Integer将comboBox5.Text解析为int：

cmd.Parameters.AddWithValue("@teller", OleDbType.Integer).Value = int.Parse(comboBox5.Text);

Answer 2

OleDb does not support named parameters. It only supports positional parameters. You need to add your parameters in the same order as they appear in the query:

cmd.Parameters.AddWithValue("@grade", OleDbType.Char).Value = textBox7.Text;
cmd.Parameters.AddWithValue("@comments", OleDbType.Char).Value = textBox10.Text;
cmd.Parameters.AddWithValue("@teller", OleDbType.Integer).Value = comboBox5.Text;
cmd.Parameters.AddWithValue("@test", OleDbType.Char).Value = comboBox16.Text;