Question

vb为什么老说else没有if

Private Sub Command2_Click(Index As Integer)
If Index = 0 Then Text1.Text = ""
ElseIf signfleg = True Then
Select Case c
Case 1
Text1.Text = a + b
Case 2
Text1.Text = a - b
Case 3
Text1.Text = a * b
Case 4
Text1.Text = a / b
End Select
End if

Answer 1

If Index = 0 Then Text1.Text = "" --- 这是完整的单行IF结构
ElseIf signfleg = True Then --- 此处的ElseIf当然缺少IF了

修改成

If Index = 0 Then
Text1.Text = ""
ElseIf signfleg = True Then

Answer 2

If 条件1 Then
语句1
ElseIf 条件2 Then
语句2
End If
上述是If块结构得标准写法。
Private Sub Command2_Click(Index As Integer)
If Index = 0 Then
Text1.Text = ""
ElseIf signfleg = True Then
Select Case c
Case 1
Text1.Text = a + b
Case 2
Text1.Text = a - b
Case 3
Text1.Text = a * b
Case 4
Text1.Text = a / b
End Select
End If
End Sub

Answer 3

If Index = 0 Then
Text1.Text = ""
'这个要分开两行写，要不然就认为是一个单行if语句。

Answer 4

If Index = 0 Then Text1.Text = ""
ElseIf signfleg = True Then
'错误

If Index = 0 Then
Text1.Text = ""
ElseIf signfleg = True Then
'这个要分开两行写，要不然就认为是一个单行if语句。

Answer 5

其实很简单，只要你在程序最后再加一个 End If 就行了