從C＃中的Richtextbox中選擇文本

Question

我想選擇位於richtextbox文本的最後一個「{」和「}」之間的文本。 我有下一個代碼，但我有一個「LastIndexOf」函數的錯誤，我不知道如何解決它。有人能給我一些幫助嗎？

private void highlightText() 
    { 
     mRtbxOperations.SelectionStart = mRtbxOperations.Text.LastIndexOf(@"{", 1, mRtbxOperations.SelectionStart); 
     mRtbxOperations.SelectionLength = mRtbxOperations.Text.IndexOf(@"}", mRtbxOperations.SelectionStart, mRtbxOperations.Text.Length - 1); 
     mRtbxOperations.SelectionBackColor = Color.LightBlue; 
     mRtbxOperations.SelectionFont = new Font(mRtbxOperations.SelectionFont, FontStyle.Underline); 
     mRtbxOperations.SelectionLength = 0; 
    } 

LastIndexOf錯誤：

The count must be positive and must refer to a location within the string, array or collection. Parameter name: count

Answer 1

您LastIndexOf參數混亂，以及選擇的長度，你需要。減去的出發點，以獲得適當的長度：

如下我將重寫代碼。

嘗試使用簡單的版本：

int textStart = mRtbxOperations.Text.LastIndexOf(@"{", 
               mRtbxOperations.SelectionStart); 
if (textStart > -1) { 
    int textEnd = mRtbxOperations.Text.IndexOf(@"}", textStart); 
    if (textEnd > -1) { 
    mRtbxOperations.Select(textStart, textEnd - textStart + 1); 
    mRtbxOperations.SelectionBackColor = Color.LightBlue; 
    } 
} 

的[RichTextBox中選擇性着色文本]

Answer 2

看來你要出來的文字界。當你得到一個子字符串或一個索引時，你總是應該使用字符串邊界或者子字符串邊界。此外，您需要檢查選擇是否有效。

private void highlightText() 
    { 
     Selection selection = GetSelection(mRtbxOperations.Text); 
     if (selection == null) 
      return; 
     mRtbxOperations.SelectionStart = selection.Start; 
     mRtbxOperations.SelectionLength = selection.Length; 
     mRtbxOperations.SelectionBackColor = Color.LightBlue; 
     mRtbxOperations.SelectionFont = new Font(mRtbxOperations.SelectionFont, 
      FontStyle.Underline); 
    } 

    private static Selection GetSelection(string text) 
    { 
     int sIndex = text.LastIndexOf(@"{"); 
     if (sIndex == -1) 
      return null; 
     int eIndex = text.IndexOf(@"}", sIndex); 
     if (eIndex == -1) 
      return null; 

     return new Selection(sIndex + 1, eIndex); 
    } 

    public class Selection 
    { 
     public int Start { get; set; } 
     public int End { get; set; } 

     public int Length 
     { 
      get 
      { 
       return End - Start; 
      } 
     } 

     public Selection(int startIndex, int endIndex) 
     { 
      this.Start = startIndex; 
      this.End = endIndex; 
     } 
    }