如何使用 C# 在 SQL 服务器数据库中保存 DataGridViewComboBoxColumn

Question

I am going to develop school management system and want to save attendance record in database from DataGridViewComboBoxColumn each student in class with Save button.

I means set all student record eg present, absent or leave the save record in database when the "save" button is pressed.

This is my code - it works when I change cell of 1st student

private void AttendanceDataGridVies_CurrentCellDirtyStateChanged(object sender, EventArgs e)
    {
        AttendanceDataGridVies.CommitEdit(DataGridViewDataErrorContexts.Commit);
    }

    private void AttendanceDataGridVies_CellValueChanged(object sender, DataGridViewCellEventArgs e)
    {
        string comboboxSelectedValue = string.Empty;

        if (AttendanceDataGridVies.Columns[e.ColumnIndex].GetType() == typeof(DataGridViewComboBoxColumn))
        {
            comboboxSelectedValue = AttendanceDataGridVies.Rows[e.RowIndex].Cells[e.ColumnIndex].Value.ToString();
            label2.Text = comboboxSelectedValue;
        }
    }

Answer 1

You probably want to set up something like Entity Framework to handle the database functions. This article is several years old now, but I think it can probably get you on your way: Entity-Framework-Tutorial-for-Beginners

Also, typically, you would want to separate the DB layer from your presentation layer. However, you can set up your own connection strings and write your own SQL instead, if you would like. To do so, you basically need to:

1. Setup a connection string
2. Create a SQL statement
3. Open SQL connection
4. Call SQL command
5. Close the connection

A very simple example connecting to a local SQL MDF inside the project:

       private void button1_Click(object sender, EventArgs e)
        {
            addToDatabase();
        }

        private void addToDatabase()
        {
            string connection = @"Server=(LocalDB)\MSSQLLocalDB;attachdbfilename=C:\Users\xxxxx\source\repos\MySolution\MyProject\MyDatabase.mdf;integrated security=True;";
            SqlConnection sqlConnection = new SqlConnection(connection);

            string query = "INSERT INTO Table1 " +
                "(Id, Column1, Column2) " +
                "VALUES (@Id,  @Column1, @Column2) ";
            SqlCommand cmd = new SqlCommand(query, sqlConnection);
            cmd.Parameters.Add("@Id", SqlDbType.Int).Value = 1;
            cmd.Parameters.Add("@Column1", SqlDbType.VarChar, 50).Value = "value1";
            cmd.Parameters.Add("@Column2", SqlDbType.VarChar, 50).Value = "Value2";

            try
            {
                sqlConnection.Open();
                cmd.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                sqlConnection.Close();
            }
        }