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");

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[点击此处收藏本文] 发表于 2005年02月18日 3:53 PM

sam 发表于2005-02-19 10:07 PM IP: 218.70.110.*

看来第一种办法最有简单。

冰戈 发表于2005-02-20 9:26 AM IP: 220.163.28.*

第一种办法效率不高,建议不用

Ofei 发表于2005-03-12 5:43 PM IP: 219.137.251.*

第二种和第三种方法都没有判断数值范围

用"99999999999999999999"作为参数 判断IsInteger()再用int.Pase()的话定会出错

用"9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"作为参数
判断IsNumber() 再用double.Parse()的话也肯定出错