当我尝试填充组合框时，它不填充

Question

早些时候，我能够填充组合框取决于另一个组合框选择，然后我继续编写代码，然后我再回来测试它再次，它不再填充该列表，它与另一个列表一起使用，但其中一个不包含。所以它填充饮料，但不是主要的。我不确定发生了什么事情，这一切对我来说似乎都没有问题。

Public Shared cmbCatDrinks As String = "Drinks" 
Public Shared cmbCatMain As String = "Main" 
Public Shared cmbCatBlank As String = "" 
Public Shared cmbItemBlank As String = "" 

Private Sub frmRestaurantOrd_Load(sender As Object, e As EventArgs) Handles MyBase.Load 
    cmbCat.Items.Add(cmbCatBlank) 
    cmbCat.Items.Add(cmbCatDrinks) 
    cmbCat.Items.Add(cmbCatMain) 
End Sub 

Private Sub cmbCat_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cmbCat.SelectedIndexChanged 
    If cmbCat.SelectedItem = "Drinks" Then 
     cmbItem.Items.Add("Water") 
     cmbItem.Items.Add("Orange Juice") 
     cmbItem.Items.Add("Coca Cola") 
     cmbItem.Items.Add("Beer") 
     cmbSize.Items.Clear() 
    ElseIf cmbCat.SelectedItem = "Main" Then 
     cmbItem.Items.Add("Cheese and Tomato") 
     cmbItem.Items.Add("Ham and Pineapple") 
     cmbItem.Items.Add("Vegetarian") 
     cmbItem.Items.Add("Meat Feast") 
     cmbItem.Items.Add("Seafood") 
     cmbSize.Items.Add("Small") 
     cmbSize.Items.Add("Medium") 
     cmbSize.Items.Add("Large") 
     cmbItem.Items.Clear() 
    Else cmbCat.SelectedItem = cmbCatBlank 
     cmbItem.Items.Clear() 
    End If 
End Sub 

Answer 1

您正在清理时，选择“主”刚才添加到cmbItem的项目。

ElseIf cmbCat.SelectedItem = "Main" Then 
    cmbItem.Items.Add("Cheese and Tomato") 
    cmbItem.Items.Add("Ham and Pineapple") 
    cmbItem.Items.Add("Vegetarian") 
    cmbItem.Items.Add("Meat Feast") 
    cmbItem.Items.Add("Seafood") 
    cmbSize.Items.Add("Small") 
    cmbSize.Items.Add("Medium") 
    cmbSize.Items.Add("Large") 
    cmbItem.Items.Clear() ' <-- this is clearing all the items you just added.