使用正则表达式限制TextBox输入

    /// <summary>
    ///  使用正则表达式限制输入
    /// </summary>
    public class TextBoxRegex : TextBox
    {
        // 正则表达式，只含有汉字、数字、字母、下划线不能以数字开头 
        private const string NamimgPattern = "^(?![0-9])[a-zA-Z0-9_\u4e00-\u9fa5]{1,30}$";

        public TextBoxRegex()
        {
            TextChanged += TextBoxRegex_TextChanged;
        }

        private void TextBoxRegex_TextChanged(object sender, TextChangedEventArgs e)
        {
            //屏蔽非法字符粘贴
            var textBox = sender as TextBox;
            if (textBox != null)
            {
                var change = new TextChange[e.Changes.Count];
                e.Changes.CopyTo(change, 0);

                int offset = change[0].Offset;
                if (change[0].AddedLength > 0)
                {
                    if (!Regex.IsMatch(textBox.Text, NamimgPattern, RegexOptions.IgnoreCase))
                    {
                        // 不符合正则表达式时移除内容，设置光标位置
                        textBox.Text = textBox.Text.Remove(offset, change[0].AddedLength);
                        textBox.Select(offset, 0);
                    }
                }
            }
        }
    }