C# 字符串扩展方法

功能

1.判断一个字符串是否为null或者空字符串

2.判断一个字符串是否为null或者空白字符

3.判断一个字符串是否为数字

4.判断一个字符串是否为邮件

5.判断一个字符串是否为字母加数字

6.判断一个字符串是否为手机号码

7.判断一个字符串是否为电话号码

8.判断一个字符串是否为网址

9.判断一个字符串是否为IP地址

10.判断是否为字母

转换

11.string 转 int

12.string 转 ushort

13.string 转 float

string 转 double

截取

14.获取指定长度字符串的值

15.清除SQL注入的危险字符

16.根据path递规创建文件夹

优点

1.一定编写随处可用。

2.调用代码简单，代码量少。

3.成熟代码无BUG

我是封装到DLL文件中，在具体的项目中引用。

引用命令空间

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Web.Security;

代码

/// <summary>
/// 字符串扩展方法
/// </summary>
public static class StringExtension
{
    #region 常量定义
    //数字
    private const string REGEX_NUMERIC = @"^[-]?\d+[.]?\d*$";
    //邮件
    private const string REGEX_EMAIL = @"^\w+([-+.]\w+)*@(\w+([-.]\w+)*\.)+([a-zA-Z]+)+$";
    //中文字符
    private const string REGEX_CHINESE_CHARACTER = @"^[\u4e00-\u9fa5]{0,}$";
    #endregion

    #region 判断
    /// <summary>
    /// 判断一个字符串是否为null或者空字符串
    /// </summary>
    /// <param name="str">要判断的字符串</param>
    /// <returns>true: 空或者空字符串,false:不为空或者空字符串</returns>
    public static bool IsNullOrEmpty(this string str)
    {
        return string.IsNullOrEmpty(str);
    }

    /// <summary>
    /// 判断一个字符串是否为null或者空白字符
    /// </summary>
    /// <param name="str">要判断的字符串</param>
    /// <returns>true: 空或者空字符串,false:不为空或者空白字符</returns>
    public static bool IsNullOrWhiteSpace(this string str)
    {
        return string.IsNullOrWhiteSpace(str);
    }

    /// <summary>
    /// 判断一个字符串是否为数字
    /// </summary>
    /// <param name="str">待检测字符串</param>
    /// <returns>true: 输入字符串是合法数字，false: 输入字符串不是合法数字，空字符串返回false</returns>
    public static bool IsNumeric(this string str)
    {
        if (str == null) return false;
        if (string.IsNullOrEmpty(str))
        {
            return false;
        }
        str = str.Replace(",", String.Empty);
        Regex regNum = new Regex(REGEX_NUMERIC);
        return regNum.IsMatch(str);
    }

    /// <summary>
    /// 判断一个字符串是否为邮件
    /// </summary>
    /// <param name="str">待检测字符串</param>
    /// <returns>true: 输入字符串是合法邮件地址，false：输入字符串不是合法邮件地址，空字符串返回false</returns>
    public static bool IsEmail(this string str)
    {
        if (str == null) return false;
        Regex regex = new Regex(REGEX_EMAIL, RegexOptions.IgnoreCase);
        return regex.Match(str).Success;
    }

    /// <summary>
    /// 判断一个字符串是否为字母加数字
    /// Regex("[a-zA-Z0-9]?"
    /// </summary>
    /// <param name="str"></param>
    /// <returns></returns>
    public static bool IsWordAndNum(this string str)
    {
        Regex regex = new Regex("[a-zA-Z0-9]?");
        return regex.Match(str).Success;
    }

    /// <summary>
    /// 判断一个字符串是否为手机号码
    /// </summary>
    /// <param name="str">待检测字符串</param>
    /// <returns>true: 输入字符串是合法的手机号码，false: 输入字符串不是合法的手机号码，空字符串返回false</returns>
    public static bool IsMobileNum(this string str)
    {
        if (str == null) return false;
        Regex regex = new Regex(@"^(13[0-9]|15[0-9]|18[0-9]|147|17[0-9])\d{8}$", RegexOptions.IgnoreCase);
        return regex.Match(str).Success;
    }

    /// <summary>
    /// 判断一个字符串是否为电话号码
    /// </summary>
    /// <param name="str">待检测字符串</param>
    /// <returns>true: 输入字符串是合法的电话号码，false: 输入字符串不是合法的电话号码，空字符串返回false</returns>
    public static bool IsPhoneNum(this string str)
    {
        if (str == null) return false;
        Regex regex = new Regex(@"^(86)?(-)?(0\d{2,3})?(-)?(\d{7,8})(-)?(\d{3,5})?$", RegexOptions.IgnoreCase);
        return regex.Match(str).Success;
    }

    /// <summary>
    /// 判断一个字符串是否为网址
    /// </summary>
    /// <param name="str">待检测字符串</param>
    /// <returns>true: 输入字符串是合法的网址，false: 输入字符串不是合法的网址，空字符串返回false</returns>
    public static bool IsUrl(this string str)
    {
        if (str == null) return false;
        Regex regex = new Regex(@"(http://)?([\w-]+\.)*[\w-]+(/[\w- ./?%&=]*)?", RegexOptions.IgnoreCase);
        return regex.Match(str).Success;
    }

    /// <summary>
    /// 判断一个字符串是否为IP地址
    /// </summary>
    /// <param name="str">待检测字符串</param>
    /// <returns>true: 输入字符串是合法的IP地址，false: 输入字符串不是合法的IP地址，空字符串返回false</returns>
    public static bool IsIp(this string str)
    {
        if (str == null) return false;
        Regex regex = new Regex(@"^(((2[0-4]{1}[0-9]{1})|(25[0-5]{1}))|(1[0-9]{2})|([1-9]{1}[0-9]{1})|([0-9]{1})).(((2[0-4]{1}[0-9]{1})|(25[0-5]{1}))|(1[0-9]{2})|([1-9]{1}[0-9]{1})|([0-9]{1})).(((2[0-4]{1}[0-9]{1})|(25[0-5]{1}))|(1[0-9]{2})|([1-9]{1}[0-9]{1})|([0-9]{1})).(((2[0-4]{1}[0-9]{1})|(25[0-5]{1}))|(1[0-9]{2})|([1-9]{1}[0-9]{1})|([0-9]{1}))$", RegexOptions.IgnoreCase);
        return regex.Match(str).Success;
    }

    /// <summary>
    /// 判断是否为字母
    /// </summary>
    /// <param name="str">要校验的字符串</param>
    /// <returns></returns>
    public static bool IsLetters(this string str)
    {
        if (str == null) return false;
        return Regex.IsMatch(str, @"^[a-zA-Z]");
    }

    /// <summary>
    /// 判断密码是否符合规则
    /// </summary>
    /// <param name="str"></param>
    /// <returns></returns>
    public static bool IsPassword(this string str, string pattern = "^[a-zA-Z0-9_]{6,18}$")
    {
        if (str == null) return false;
        return Regex.IsMatch(str, @"" + pattern + "");
    }
    #endregion

    #region 转换
    /// <summary>
    /// string 转 int
    /// </summary>
    /// <param name="value"></param>
    /// <returns>转换失败返回int最小值，否则返回对应的值</returns>
    public static int ToInt(this string value)
    {
        int val = int.MinValue;
        int.TryParse(value, out val);
        return val;
    }

    /// <summary>
    /// string 转 int
    /// </summary>
    /// <param name="value"></param>
    /// <param name="defaultVal">转换失败的默认值</param>
    /// <returns>转换失败返回int最小值，否则返回对应的值</returns>
    public static int ToInt(this string value,int defaultVal = int.MinValue)
    {
        int val = defaultVal;
        int.TryParse(value, out val);
        return val;
    }

    /// <summary>
    /// string 转 ushort
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public static ushort ToUshort(this string value)
    {
        return ushort.Parse(value.ToString());
    }

    /// <summary>
    /// string 转 float
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public static float ToFloat(this string value)
    {
        return float.Parse(value);
    }

    /// <summary>
    /// string 转 double
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public static double ToDouble(this string value)
    {
        double val = double.MinValue;
        double.TryParse(value,out val);
        return val;
    }
    #endregion

    #region 截取
    /// <summary>
    /// 获取指定长度字符串的值
    /// </summary>
    /// <param name="str"></param>
    /// <param name="length">指定长度</param>
    /// <returns></returns>
    public static string GetAssignLenVal(this string str, int length = 10)
    {
        string returnVal = string.Empty;
        if (!string.IsNullOrEmpty(str))
        {
            returnVal = str.Length > length ? string.Format("{0}...", str.Substring(0, length)) : str;
        }
        return returnVal;
    }

    /// <summary>
    /// 截取字符串
    /// 如果转入的是null或''都返返回，string.Empty
    /// </summary>
    /// <param name="sourceStr">源字符串</param>
    /// <param name="length">最大长度</param>
    /// <returns>新字符串</returns>
    public static string SubstringExtend(this string sourceStr, int length)
    {
        string resultStr = string.Empty;
        if (!string.IsNullOrEmpty(sourceStr))
        {
            resultStr = sourceStr;
            if (sourceStr.Length >= length)
            {
                resultStr = sourceStr.Substring(0, length - 1);
            }
        }
        return resultStr;
    }

    #endregion

    /// <summary>
    /// 清除SQL注入的危险字符
    /// </summary>
    /// <param name="str"></param>
    /// <returns></returns>
    public static string ClearDangerStr(this string str)
    {
        return str.ToLower().Replace("'", string.Empty).Replace(";", string.Empty).Replace("-", string.Empty).Replace("$", string.Empty).Replace(@"\", string.Empty).Replace(@"/", string.Empty)
            .Replace("delete", string.Empty).Replace("update", string.Empty).Replace("drop", string.Empty).Replace("insert", string.Empty).Replace("select", string.Empty)
            .Replace("alter", string.Empty).Replace("create", string.Empty);
    }

    /// <summary>
    /// 根据path递规创建文件夹
    /// </summary>
    /// <param name="filePath"></param>
    /// <returns></returns>
    public static bool CreateDirectoryByPath(this string filePath)
    {
        var isOk = false;
        var filePathDirectory = filePath.Substring(0, filePath.LastIndexOf(@"\"));
        filePathDirectory = filePathDirectory.Replace("//", @"\").Replace("/", @"\");
        var directory = filePathDirectory.Split('\\').ToList();
        var existsDir = string.Empty;
        foreach (var item in directory)
        {
            existsDir += item + @"\";
            if (!Directory.Exists(existsDir))
            {
                Directory.CreateDirectory(existsDir);
            }
        }
        isOk = true;
        return isOk;
    }
}