如何在RichTextBox中使用指定字符拼接选中行并替换原有行

实现逻辑 #

• 定位选中内容对应的起始行、结束行索引，提取选中范围内的所有行文本
• 用指定分隔符拼接所有提取到的行文本
• 替换原有选中的多行内容为拼接后的新行

代码实现（C# WinForm） #

// 入参：目标RichTextBox控件，自定义拼接分隔符
public void ConcatSelectedLines(RichTextBox richTextBox, string separator)
{
    richTextBox.SuspendLayout();

    // 获取选中区域对应的起止行索引
    int startLine = richTextBox.GetLineFromCharIndex(richTextBox.SelectionStart);
    int endLine = richTextBox.GetLineFromCharIndex(richTextBox.SelectionStart + richTextBox.SelectionLength);

    // 收集选中行内容，TrimEnd处理行尾换行符
    List<string> selectedLines = new List<string>();
    for (int i = startLine; i <= endLine; i++)
    {
        selectedLines.Add(richTextBox.Lines[i].TrimEnd('\r', '\n'));
    }

    // 拼接得到新行
    string mergedLine = string.Join(separator, selectedLines);

    // 计算要替换的字符范围
    int replaceStartIndex = richTextBox.GetFirstCharIndexFromLine(startLine);
    int replaceLength;
    if (endLine < richTextBox.Lines.Length - 1)
    {
        replaceLength = richTextBox.GetFirstCharIndexFromLine(endLine + 1) - replaceStartIndex;
    }
    else
    {
        replaceLength = richTextBox.TextLength - replaceStartIndex;
    }

    // 执行替换
    richTextBox.Select(replaceStartIndex, replaceLength);
    richTextBox.SelectedText = mergedLine;

    richTextBox.ResumeLayout();
}

调用示例 #

如果你要使用-作为分隔符，直接调用方法即可：
ConcatSelectedLines(yourRichTextBoxControl, " - ");

效果验证 #

原文本：

The situation is dire
But momma raised up a fighter
It's all come down to the wire
But the come-up is higher

选中前两行调用方法后，得到效果：

The situation is dire - But momma raised up a fighter
It's all come down to the wire
But the come-up is higher

选中后两行调用方法后，得到效果：

The situation is dire
But momma raised up a fighter
It's all come down to the wire - But the come-up is higher

内容的提问来源于stack exchange，提问作者vahid Araghi