只是工作中常用到对用户输入的字符串进行判断处理等，所有总结了一些方法，作为总结，亦可复用。
public sealed class CleanString
{
#region 数字字符串检查
private static Regex _isNumber = new Regex("^[0-9]+$");
//检查Request查询字符串的键值，是否是数字，最大长度限制
// return a digit string based on input data
// look first in the QueryString collection,
//then in Form return string.Empty if not found or if non-digit
public static string FetchInputDigit(HttpRequest req, string inputKey, int maxLen)
{
string retVal = string.Empty;
if(inputKey != null && inputKey != string.Empty)
{
retVal = req.QueryString[inputKey];
if(null == retVal)
retVal = req.Form[inputKey];
if(null != retVal)
{
retVal = CleanString.SqlText(retVal, maxLen);
if(!IsNumber(retVal))
retVal = string.Empty;
}
}
if(retVal == null)
retVal = string.Empty;
return retVal;
}
//是否数字字符串
public static bool IsNumber(string inputData)
{
Match m = _isNumber.Match(inputData);
return m.Success;
}
//是否数字字符串
public static bool IsNumberInt(string inputData)
{
try
{
int.Parse(inputData);
}
catch
{
return false;
}
return true;
}
//是否数字字符串
public static bool IsNumberDecimal(string inputData)
{
try
{
decimal.Parse(inputData);
}
catch
{
return false;
}
return true;
}
//字符串编码
public static string HtmlEncode(string inputData)
{
return HttpUtility.HtmlEncode(inputData);
}
public static void SetLabel(Label lbl, string txtInput)
{
lbl.Text = HtmlEncode(txtInput);
}
public static void SetLabel(Label lbl, object inputObj)
{
SetLabel(lbl, inputObj.ToString());
}
/// <summary>
/// 检查字符串最大长度，返回指定长度的串
/// </summary>
/// <param name="sqlInput">输入字符串</param>
/// <param name="maxLength">最大长度</param>
/// <returns></returns>
public static string SqlText(string sqlInput, int maxLength)
{
if(sqlInput != null && sqlInput != string.Empty)
{
sqlInput = sqlInput.Trim();
if(sqlInput.Length > maxLength)//按最大长度截取字符串
sqlInput = sqlInput.Substring(0, maxLength);
}
return sqlInput;
}
#endregion
//字符串清理
public static string InputText(string inputString, int maxLength)
{
StringBuilder retVal = new StringBuilder();
// 检查是否为空
if ((inputString != null) && (inputString != String.Empty))
{
inputString = inputString.Trim();
//检查长度
if (inputString.Length > maxLength)
inputString = inputString.Substring(0, maxLength);
//替换危险字符
for (int i = 0; i < inputString.Length; i++)
{
switch (inputString[i])
{
case '"':
retVal.Append(""");
break;
case '<':
retVal.Append("<");
break;
case '>':
retVal.Append(">");
break;
default:
retVal.Append(inputString[i]);
break;
}
}
// 替换单引号
retVal.Replace("'", " ");
}
return retVal.ToString();
}
} | 
