做直到循环检查重复不会停止循环

Question

我试图做一个直到循环来检查我的组合框中的重复项。它运行循环，但它永远不会停止循环。

Dim i As Integer = 0 
    Dim flavors As Integer = flavorsComboBox.Items.Count 

    Do Until (i < flavors - 1) 
     If flavors = flavorsComboBox.Items.Count Then 
      MessageBox.Show("Flavor Already Exists!", "Error") 
     Else 
      flavorsComboBox.Items.Add(flavorsComboBox.Text) 
     End If 
    Loop 

Answer 1

你是不是重置口味的价值

试试这个：

Dim i As Integer = 0 
Dim flavors As Integer = flavorsComboBox.Items.Count 

Do Until (i < flavors - 1) 
    If flavors = flavorsComboBox.Items.Count Then 
     MessageBox.Show("Flavor Already Exists!", "Error") 
    Else 
     flavorsComboBox.Items.Add(flavorsComboBox.Text) 
     flavors = flavorsComboBox.Items.Count 
    End If 
Loop 

Answer 2

下面是一个简单的做，直到环

Dim i as integer = 0 
Dim flavors as Integer = 10 

do until (i > flavors -1) 
    Console.WriteLine(i.ToString()) 

    i = i +1 
loop 

输出

0 
1 
2 
3 
4 
5 
6 
7 
8 
9 

在您的代码：

do until (i < flavors - 1) 

若i = 0和口味是计数-1时大于count 0，进入循环的状态。

接下来的遗漏是，您永远不会更改循环条件变量的值，以准确评估停止循环的条件。

Answer 3

循环的条件着眼于i变量和flavors变量：

Do Until (i < flavors - 1) 

但这些变量永远不要在循环体中的任何一点变化：

If flavors = flavorsComboBox.Items.Count Then 
     MessageBox.Show("Flavor Already Exists!", "Error") 
    Else 
     flavorsComboBox.Items.Add(flavorsComboBox.Text) 
    End If 

您需要添加代码来更改其中一个或两个变量。但是，这仍然是难以实现的目标。只需使用Distinct()方法：

Dim items = flavorsComboBox.Items.Distinct().ToArray() 
flavorsComboBox.Items.Clear() 
flavorsComboBox.Items.AddRange(items) 

Answer 4

试试这个：

Option Strict On 
Option Explicit On 
Option Infer Off 
Public Class Form1 
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 
     If AddDistinct(flavorsComboBox, "test") Then 
      MsgBox("Item did not exist, so it was added.") 
     Else 
      MsgBox("Item already existed, so it was not added.") 
     End If 
    End Sub 
    Public Function AddDistinct(cboBox As ComboBox, value As Object) As Boolean 
     If cboBox.Items.IndexOf(value) = -1 Then cboBox.Items.Add(value) : Return True 
     Return False 
    End Function 
End Class