Question

我在使用此代码时遇到问题。我希望它使Textbox大写的第一个字母，但如果文本框为空，程序崩溃。我知道问题与子串的长度有关，所以如果有人能帮我解决这个问题，那就太好了！注意：文本框的名称是richTextBoxGuess，每次文本框中的文本发生更改时，此代码都会运行。

if (char.IsLower(Convert.ToChar(richTextBoxGuess.Text.Substring(0, 1))) ) // Checks if first letter is lower case
{
    richTextBoxGuess.Text = richTextBoxGuess.Text.Replace(richTextBoxGuess.Text.Substring(0, 1), richTextBoxGuess.Text.ToUpper()); // Changes first letter to uppercase
    richTextBoxGuess.SelectionStart = 2; // Puts cursor after first letter
}

Answer 1

检查richTextBoxGuess是空还是空

if( richTextBoxGuess != ""){ // or different from null
     if (char.IsLower(Convert.ToChar(richTextBoxGuess.Text.Substring(0, 1))) ){
             //your code
     }
}

Answer 2

这不会破坏以前格式的内容：

private void richTextBoxGuess _TextChanged(object sender, EventArgs e)
{
    if (richTextBoxGuess .Text.Length <= 0) return;
    string s = richTextBoxGuess.Text.Substring(0, 1);
    if (s != s.ToUpper())
    {
        int curSelStart = richTextBoxGuess.SelectionStart;
        int curSelLength = richTextBoxGuess.SelectionLength;
        richTextBoxGuess.SelectionStart = 0;
        richTextBoxGuess.SelectionLength = 1;
        richTextBoxGuess.SelectedText = s.ToUpper();
        richTextBoxGuess.SelectionStart = curSelStart;
        richTextBoxGuess.SelectionLength = curSelLength;
    }
}

请注意，它不会跟踪更改，并且在您继续添加前端时无法恢复它们。

如果您需要文化不变性，请使用CultureInfo.CurrentCulture的{{1}}参数！

Answer 3

编写此扩展方法：

public static string CapitalizeFirstLetter(this string input)
{
    if (string.IsNullOrEmpty(input))
    {
        return input;
    }

    return input.Substring(0, 1).ToUpper(CultureInfo.CurrentCulture) + input.Substring(1);
}

然后将其用作

richTextBoxGuess.Text = richTextBoxGuess.Text.CapitalizeFirstLetter();

Answer 4

 private void _capitalizeFirstWord(Object sender, KeyPressEventArgs e)
        {
           if (_richTB.Text.Trim() == String.Empty)
            {
                e.KeyChar = char.ToUpper(e.KeyChar);
            }
        }

如果你想把每个单词都大写

char _pre,_cur;
_pre=' ';
 private void _capitalizeEveryWord(Object sender, KeyPressEventArgs e)
        {
           _cur = e.KeyChar;
           if (_richTB.Text.Trim() == String.Empty)
            {
                e.KeyChar = char.ToUpper(e.KeyChar);
            }
            e.Handled = !(char.IsLetter(e.KeyChar) || e.KeyChar == (char)Keys.Back || e.KeyChar == ' ' && (!(_cur == _pre)) || e.KeyChar == '.' &&                  (!(_pre == _cur)));
            _pre=_cur

        }

制作文本框大写的第一个字母

4 个答案: