[.NET] 如何寫入資料庫

[su35 (su35)]

我用vb2005.net 開ms sql的資料庫 檔名cNorthWind.mdf
表單名稱 員工

問題一Dim da As New SqlClient.SqlDataAdapter(SQL, conn)
Dim dc As New SqlClient.SqlCommand(SQL, conn)
這兩個有什麼不同   一樣都是SQL語法  還是說一個只有查詢   一個是加入刪除的功能

問題二  DBACCRESS.ExecuteCmd(....,.....)
{
這涵數   當parameters有值的話  它到底做了什麼事
parameters  它儲存什麼東西
}

問題三
我在Button2  做了把第一列的欄位資料刪除
它在不關掉程式 的確那欄資料不見了
可是根本沒寫入到資料庫內
為什麼會這樣  還有要怎麼樣才能寫進去


感謝




Public Class Form1
    Dim DB As DbAccess
    Dim DT As New DataTable

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        UpData()
    End Sub

    Sub UpData()
        DB = New DbAccess("cNorthWind.mdf")
        DT = DB.GetDataTable("select * from 員工")
        DB = Nothing
        DataGridView1.DataSource = DT   '將DataTable 傳給DataGridView
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        DB = New DbAccess("cNorthWind.mdf")
        DT = DB.GetDataTable("select * from 員工 where 員工編號 = '" & TextBox1.Text & "'")
        DataGridView1.DataSource = DT
        DB = Nothing
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        SQL_string = "delete from 員工 where 員工編號 = '1'"
        DB = New DbAccess("cNorthWind.mdf")
        DB.ExecuteCmd(SQL_string)
        DB = Nothing
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        DB = New DbAccess("cNorthWind.mdf") '建立資料庫連線
        DT = DB.GetDataTable("select * from 員工")  '寫sql 讀取資料到DataTable
        DB = Nothing    '解除物件
        DataGridView1.DataSource = DT   '將DataTable 傳給DataGridView
    End Sub

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        DB = New DbAccess("cNorthWind.mdf") '建立資料庫連線
        DT = DB.GetDataTable("select * from 員工")  '寫sql 讀取資料到DataTable
        Dim DA As DataAdapter
        DA.Update(DS)



    End Sub
End Class




















Public Class DbAccess
    Private conn As SqlClient.SqlConnection

    Private _ErrorMessage As String
    '回傳錯誤訊息
    Public Property ErrorMessage() As String
        Get
            Return _ErrorMessage
        End Get
        Set(ByVal value As String)
            _ErrorMessage = value
        End Set
    End Property


    Sub New(ByVal SqlExpressDbName As String)
        '建立連線
        If System.IO.Path.GetDirectoryName(SqlExpressDbName) = "" Then
            conn = New SqlClient.SqlConnection("Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\" & SqlExpressDbName & ";Integrated Security=True;User Instance=True")
        Else
            conn = New SqlClient.SqlConnection("Data Source=.\SQLEXPRESS;AttachDbFilename=" & SqlExpressDbName & ";Integrated Security=True;User Instance=True")
        End If
    End Sub

    '讀取資料
    Function GetDataTable(ByVal SQL As String) As DataTable
        Try
            Dim dt As New DataTable
            Dim da As New SqlClient.SqlDataAdapter(SQL, conn)
            da.Fill(dt)

            Return dt
        Catch ex As Exception
            MsgBox("讀取資料時發生錯誤(" & SQL & ") " & vbCrLf & "錯誤訊息:" & ex.Message, MsgBoxStyle.Critical)
            Return Nothing
        End Try
    End Function

    '執行命令
    Function ExecuteCmd(ByVal SQL As String) As Integer
        Return ExecuteCmd(SQL, Nothing)
    End Function
    '執行命令
    Function ExecuteCmd(ByVal SQL As String, ByVal parameters As SqlClient.SqlParameterCollection) As Integer
        Try
            If conn.State <> ConnectionState.Open Then conn.Open()
            Dim dc As New SqlClient.SqlCommand(SQL, conn)
            '處理參數
            If parameters IsNot Nothing Then
                dc.Parameters.Clear()
                For Each item As SqlClient.SqlParameter In parameters
                    dc.Parameters.AddWithValue(item.ParameterName, item.Value)
                Next
            End If
            '執行
            Return dc.ExecuteNonQuery
        Catch ex As Exception
            MsgBox("執行命令時發生錯誤(" & SQL & ") " & vbCrLf & "錯誤訊息:" & ex.Message, MsgBoxStyle.Critical)
            Return Nothing
        End Try
    End Function
End Class

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