使用 .net 从 MS Access 数据库中删除不存在的记录

问题描述

以下函数从我的 MS Access 数据库中删除该行。一切正常，只是如果我输入一个不存在的“txtRiskid.Text”，它会运行 else 语句。我怎么能在这个 if 语句中捕捉到这个，所以如果我输入一个不存在的“txtRiskid.Text”，它会通过消息告诉我它不存在，类似于我写的如果它被留下空。

删除按钮编码：

Private Sub Deletebtn_Click_1(sender As Object,e As EventArgs) Handles Deletebtn.Click
    If txtRiskid.Text = "" Then
        MsgBox("Please enter a existing 'Risk ID' to delete the specific record from the database","Warning")
    Else
        Dim Deletequery As String = "delete from Risk_Register where ID=@ID"
        Runquery(Deletequery)
        MsgBox("The record has been Deleted successfully from the database.","information")
    End If
End Sub

运行查询编码：

Public Sub Runquery(ByVal query As String)

    con = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\ahmed\OneDrive\Desktop\ProjectDatabase2003.mdb")
    Dim cmd As New OleDbCommand(query,con)

    cmd.Parameters.AddWithValue("@ID",txtRiskid.Text)
    cmd.Parameters.AddWithValue("@Risk_Name",txtRiskname.Text)
    cmd.Parameters.AddWithValue("@Risk_Description",txtRiskdescription.Text)
    cmd.Parameters.AddWithValue("@Owner",txtOwner.Text)
    cmd.Parameters.AddWithValue("@Control",txtControl.Text)
    cmd.Parameters.AddWithValue("@Probability",txtProbability.Text)
    cmd.Parameters.AddWithValue("@Impact",txtImpact.Text)
    cmd.Parameters.AddWithValue("@Risk_Level",txtRisklevel.Text)

    con.open()
    cmd.ExecuteNonQuery()
    con.Close()

End Sub

解决方法

ExecuteNonQuery() 返回受影响的行数见 https://docs.microsoft.com/en-us/dotnet/api/system.data.oledb.oledbcommand.executenonquery 从您的 Runquery 子程序返回它并检查 Deletebtn_Click_1 处理程序。

那种

Private Sub Deletebtn_Click_1(sender As Object,e As EventArgs) Handles Deletebtn.Click
    If txtRiskid.Text = "" Then
        MsgBox("Please enter a existing 'Risk ID' to delete the specific record from the database","Warning")
    Else
        Dim Deletequery As String = "delete from Risk_Register where ID=@ID"
        If Runquery(Deletequery) > 0 Then
            MsgBox("The record has been Deleted successfully from the database.","Information")
        Else
            MsgBox("The record doesn't exist in the database.","Information")
        End If
    End If
End Sub

和

Public Function Runquery(ByVal query As String) As Integer

    con = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Users\ahmed\OneDrive\Desktop\ProjectDatabase2003.mdb")
    Dim cmd As New OleDbCommand(query,con)
    Dim count As Integer
    cmd.Parameters.AddWithValue("@ID",txtRiskid.Text)
    cmd.Parameters.AddWithValue("@Risk_Name",txtRiskname.Text)
    cmd.Parameters.AddWithValue("@Risk_Description",txtRiskdescription.Text)
    cmd.Parameters.AddWithValue("@Owner",txtOwner.Text)
    cmd.Parameters.AddWithValue("@Control",txtControl.Text)
    cmd.Parameters.AddWithValue("@Probability",txtProbability.Text)
    cmd.Parameters.AddWithValue("@Impact",txtImpact.Text)
    cmd.Parameters.AddWithValue("@Risk_Level",txtRisklevel.Text)

    con.Open()
    count = cmd.ExecuteNonQuery()
    con.Close()
    Return count
End Function