C#判断一个string是否可以为数字

方案一：Try...Catch(执行效率不高)
    /// <summary>
    /// 名称：IsNumberic
    /// 功能：判断输入的是否是数字
    /// 参数：string oText：源文本
    /// 返回值： bool true:是 false:否
    /// </summary>
    /// <param name="oText"></param>
    /// <returns></returns>
    private bool IsNumberic(string oText)
    {
        try
        {
            int var1 = Convert.ToInt32(oText);
            return true;
        }
        catch
        {
            return false;
        }
    }

方案二：正则表达式(推荐)
a)

    using System;
    using System.Text.RegularExpressions;

    public bool IsNumber(String strNumber)
    {
        Regex objNotNumberPattern = new Regex("[^0-9.-]");
        Regex objTwoDotPattern = new Regex("[0-9]*[.][0-9]*[.][0-9]*");
        Regex objTwoMinusPattern = new Regex("[0-9]*[-][0-9]*[-][0-9]*");
        String strValidRealPattern = "^([-]|[.]|[-.]|[0-9])[0-9]*[.]*[0-9]+$";
        String strValidIntegerPattern = "^([-]|[0-9])[0-9]*$";
        Regex objNumberPattern = new Regex("(" + strValidRealPattern + ")|(" + strValidIntegerPattern + ")");

        return !objNotNumberPattern.IsMatch(strNumber) &&
        !objTwoDotPattern.IsMatch(strNumber) &&
        !objTwoMinusPattern.IsMatch(strNumber) &&
        objNumberPattern.IsMatch(strNumber);
    }

b)

    public static bool IsNumeric(string value)
    {
        return Regex.IsMatch(value, @"^[+-]?\d*[.]?\d*$");
    }
    public static bool IsInt(string value)
    {
        return Regex.IsMatch(value, @"^[+-]?\d*$");
    }
    public static bool IsUnsign(string value)
    {
        return Regex.IsMatch(value, @"^\d*[.]?\d*$");
    }

方案三：遍历
a)
    public bool isnumeric(string str)
    {
        char[] ch=new char[str.Length];
        ch=str.ToCharArray();
        for(int i=0;i<ch.Length;i++)
        {
            if(ch[i]<48 || ch[i]>57)
                return false;
        }
        return true;
    }

b)
    public bool IsInteger(string strIn)
    {
        bool bolResult = true;
        if (strIn == "")
        {
            bolResult = false;
        }
        else
        {
            foreach (char Char in strIn)
            {
                if (char.IsNumber(Char))
                    continue;
                else
                {
                    bolResult = false;
                    break;
                }
            }
        }
        return bolResult;
    }

c)
    public static bool isNumeric(string inString)
    {
        inString = inString.Trim();
        bool haveNumber = false;
        bool haveDot = false;
        for (int i = 0; i < inString.Length; i++)
        {
            if (Char.IsNumber(inString[i]))
            {
                haveNumber = true;
            }
            else if (inString[i] == '.')
            {
                if (haveDot)
                {
                    return false;
                }
                else
                {
                    haveDot = true;
                }
            }
            else if (i == 0)
            {
                if (inString[i] != '+' && inString[i] != '-')
                {
                    return false;
                }
            }
            else
            {
                return false;
            }
            if (i > 20)
            {
                return false;
            }
        }
        return haveNumber;
    }

方案四：改写vb的IsNumeric源代码(执行效率不高)

//主调函数
public static bool IsNumeric(object Expression)
{
      bool flag1;
      IConvertible convertible1 = null;
      if (Expression is IConvertible)
      {
            convertible1 = (IConvertible) Expression;
      }
      if (convertible1 == null)
      {
            if (Expression is char[])
            {
                  Expression = new string((char[]) Expression);
            }
            else
            {
                  return false;
            }
      }
      TypeCode code1 = convertible1.GetTypeCode();
      if ((code1 != TypeCode.String) && (code1 != TypeCode.Char))
      {
            return Utils.IsNumericTypeCode(code1);
      }
      string text1 = convertible1.ToString(null);
      try
      {
            long num2;
            if (!StringType.IsHexOrOctValue(text1, ref num2))
            {
                  double num1;
                  return DoubleType.TryParse(text1, ref num1);
            }
            flag1 = true;
      }
      catch (Exception)
      {
            flag1 = false;
      }
      return flag1;
}

//子函数
// return Utils.IsNumericTypeCode(code1);
internal static bool IsNumericTypeCode(TypeCode TypCode)
{
      switch (TypCode)
      {
            case TypeCode.Boolean:
            case TypeCode.Byte:
            case TypeCode.Int16:
            case TypeCode.Int32:
            case TypeCode.Int64:
            case TypeCode.Single:
            case TypeCode.Double:
            case TypeCode.Decimal:
            {
                  return true;
            }
            case TypeCode.Char:
            case TypeCode.SByte:
            case TypeCode.UInt16:
            case TypeCode.UInt32:
            case TypeCode.UInt64:
            {
                  break;
            }
      }
      return false;
}

//-----------------
//StringType.IsHexOrOctValue(text1, ref num2))
internal static bool IsHexOrOctValue(string Value, ref long i64Value)
{
      int num1;
      int num2 = Value.Length;
      while (num1 < num2)
      {
            char ch1 = Value[num1];
            if (ch1 == ´&´)
            {
                  ch1 = char.ToLower(Value[num1 + 1], CultureInfo.InvariantCulture);
                  string text1 = StringType.ToHalfwidthNumbers(Value.Substring(num1 + 2));
                  if (ch1 == ´h´)
                  {
                        i64Value = Convert.ToInt64(text1, 0x10);
                  }
                  else if (ch1 == ´o´)
                  {
                        i64Value = Convert.ToInt64(text1, 8);
                  }
                  else
                  {
                        throw new FormatException();
                  }
                  return true;
            }
            if ((ch1 != ´ ´) && (ch1 != ´\u3000´))
            {
                  return false;
            }
            num1++;
      }
      return false;
}
//----------------------------------------------------
// DoubleType.TryParse(text1, ref num1);
internal static bool TryParse(string Value, ref double Result)
{
      bool flag1;
      CultureInfo info1 = Utils.GetCultureInfo();
      NumberFormatInfo info3 = info1.NumberFormat;
      NumberFormatInfo info2 = DecimalType.GetNormalizedNumberFormat(info3);
      Value = StringType.ToHalfwidthNumbers(Value, info1);
      if (info3 == info2)
      {
            return double.TryParse(Value, NumberStyles.Any, info2, out Result);
      }
      try
      {
            Result = double.Parse(Value, NumberStyles.Any, info2);
            flag1 = true;
      }
      catch (FormatException)
      {
            flag1 = double.TryParse(Value, NumberStyles.Any, info3, out Result);
      }
      catch (Exception)
      {
            flag1 = false;
      }
      return flag1;
}

方案五： 直接引用vb运行库(执行效率不高)

方法： 首先需要添加Visualbasic.runtime的引用
代码中Using Microsoft.visualbasic;
程序中用Information.isnumeric("ddddd");

出处：http://blog.csdn.net/fredlau/archive/2007/12/24/1964989.aspx

System.Text.RegularExpressions.Regex reg1 
       = new System.Text.RegularExpressions.Regex(@"^[-]?\d+[.]?\d*$");  
   return reg1.IsMatch(str);