C＃CheckedListBox在foreach循环上的InvalidOperationException

问题描述：

我不知道我在做什么错，但我不断收到此错误。有谁知道这可能是什么原因造成的？C＃CheckedListBox在foreach循环上的InvalidOperationException

InvalidOperationException 该枚举器绑定的列表已被修改。仅当列表不更改时才能使用枚举数。

public static string[] WRD = new string[] {"One","Two","Three","Four"} 

    public static string[] SYM = new string[] {"1","2","3","4"} 

    //this is how I'm populating the CheckedListBox 
    private void TMSelectionCombo_SelectedIndexChanged(object sender, EventArgs e) 
    { 
     TMSelection.Items.Clear(); 
     switch (TMSelectionCombo.SelectedItem.ToString()) 
     { 
      case "Words": 
       foreach (string s in WRD) 
       { 
        TMSelection.Items.Add(s); 
       } 
       break; 
      case "Symbols": 
       foreach (string s in SYM) 
       { 
        TMSelection.Items.Add(s); 
       } 
       break; 
     } 
    } 

    //this is where the problem is 
    private void AddTMs_Click(object sender, EventArgs e) 
    { 
     //on this first foreach the error is poping up 
     foreach (Object Obj in TMSelection.CheckedItems) 
     { 
      bool add = true; 
      foreach (Object Obj2 in SelectedTMs.Items) 
      { 
       if (Obj == Obj2) 
        add = false; 
      } 
      if (add == true) 
       TMSelection.Items.Add(Obj); 
     } 
    }

什么是TMSelection？这可能是因为你在foreach循环中添加了一个项目。 – 2012-02-14 22:06:56

答

的枚举，如果列表不改变，只能使用。

烨

创建的要添加，然后加入你要修改的列表列表什么其他列表。

像这样：

List toAdd = new List() 
for(Object item in list) { 
    if(whatever) { 
     toAdd.add(item); 
    } 
} 
list.addAll(toAdd);

答

不能更改TMSelection列举的项目。

例

List<string> myList = new List<string>(); 

foreach (string a in myList) 
{ 
    if (a == "secretstring") 
     myList.Remove("secretstring"); // Would throw an exception because the list is being enumerated by the foreach 
}

要解决此问题，使用临时表。

例

List<string> myList = new List<string>(); 
List<string> myTempList = new List<string>(); 

// Add the item to a temporary list 
foreach (string a in myList) 
{ 
    if (a == "secretstring") 
     myTempList.Add("secretstring"); 
} 

// To remove the string 
foreach (string a in myTempList) 
{ 
    myList.Remove(a); 
}

因此，在你〔实施例，添加新的项目到一个临时目录，然后foreach循环后的每个项目添加到主列表。

C＃CheckedListBox在foreach循环上的InvalidOperationException

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