คือผมอยากทราบว่าทำโปรแกรมตัดเกรดแบบ 20 คนโดยรับข้อมูลจาก Textbox มีวิธีเขียนอย่างไงครับ

Imports System.Data
Imports System.Data.SqlClient

Private Sub btnCalculateGrade_Click(sender As Object, e As EventArgs) Handles btnCalculateGrade.Click
    Call SetData()
End Sub

Private Sub SetData()
    Dim cn As String = "Data Source=PC-Name;Initial Catalog=DB_Name;User ID=sa;Password=123"
    Using Conn As New SqlConnection(cn)
        Conn.Open()
        Using tr As SqlTransaction = Conn.BeginTransaction()
            Try
                Using cmd As SqlCommand = Conn.CreateCommand()
                    cmd.CommandType = CommandType.Text
                    cmd.CommandText = <sql>
                                           UPDATE tblGrade
                                           SET tblGrade.Grade = CASE 
                                           		WHEN tblGrade.Total >= 90.0
                                           			THEN 'A'
                                           		WHEN tblGrade.Total >= 80.0
                                           			THEN 'B'
                                           		WHEN tblGrade.Total >= 70.0
                                           			THEN 'C'
                                           		WHEN tblGrade.Total >= 60.0
                                           			THEN 'D'
                                           		WHEN tblGrade.Total >= 50.0
                                           			THEN 'E'				
                                           		ELSE 'F'
                                           		END
                                      </sql>.ToString()
                    cmd.Transaction = tr
                    cmd.ExecuteNonQuery()
                    tr.Commit()
                End Using
            Catch ex As Exception
                tr.Rollback()
            End Try
        End Using
    End Using
End Sub