Question

我正在尝试在第二个IF条件或ElseIf中读取我的数据库字段，但它似乎无法正常工作。这就像我试图验证某个学生是否在某个部分列表中具有相同的位置，或者某个学生已经在另一个部分列表中并且无法在其他部分列表中运行。

代码：

cmd.CommandText = " SELECT * FROM candidate WHERE cpos='" & ComboBox1.Text & "' AND cparty='" & ComboBox2.Text & "'"
    dr = cmd.ExecuteReader

    If dr.HasRows Then
        MessageBox.Show("Position in that partylist already exist", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
    ElseIf dr("cfname") = TextBox2.Text And dr("cmname") = TextBox3.Text And dr("clname") = TextBox4.Text Then
        MessageBox.Show("Student is currently in another partylist", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
    Else
        'Success'
Endif

更新

我做了类似这样的事情

cmd.CommandText = " SELECT * FROM candidate WHERE cpos='" & ComboBox1.Text & "' AND cparty='" & ComboBox2.Text & "'; SELECT * FROM candidate WHERE cfname='" & TextBox2.Text & "' AND cmname='" & TextBox3.Text & "' AND clname='" & TextBox4.Text & "' "

    If dr.HasRows Then
        MessageBox.Show("Position in that partylist already exist", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
    dr.NextResult()
    End If
    If dr.HasRows Then
        MessageBox.Show("Student is currently in another position", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
End If

它的工作权利，但另一件事是当我触发第一个IF和第二个IF也触发时，我知道会发生但我不知道该怎么做，如果我'将第二个IF变为ElseIf然后它不会做我想做的事情。有什么提示吗？

Answer 1

cmd.CommandText = " SELECT * FROM candidate WHERE cpos='" & ComboBox1.Text & "' AND cparty='" & ComboBox2.Text & "'; SELECT * FROM candidate WHERE cfname='" & TextBox2.Text & "' AND cmname='" & TextBox3.Text & "' AND clname='" & TextBox4.Text & "' "

这只是答案，哇！

If dr.HasRows Then
    MessageBox.Show("Position in that partylist already exist", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
ElseIF dr.NexResult Then
    MessageBox.Show("Student is currently in another position", "Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
End If

如何在VB.NET中的IF语句中检索数据库字段

1 个答案: