如何判斷一個string是否可以為數字

方案一：Try...Catch(執行效率不高)
/// <summary>
/// 名稱：IsNumberic
/// 功能：判斷輸入的是否是數字
/// 參數：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：正則表達式(推薦)
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：遍歷
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：改寫vb的IsNumeric源代碼(執行效率不高)

//主調函數
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;
}

//子函數
// 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)