C # To determine whether a string is a numeric type _c# tutorial

Scheme one: Try ... Catch (Inefficient execution)

Copy Code code as follows:

private bool Isnumberic (string otext)
{
Try
{
int Var1=convert.toint32 (otext);
return true;
}
Catch
{
return false;
}
}

Scenario Two: Regular Expressions (recommended)

A

Copy Code code as follows:

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

b

Copy Code code as follows:

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);
}

Scenario Three: Traversal

A

Copy Code code as follows:

public bool IsNumeric (string str)
{
Char[] Ch=new char[str. Length];
Ch=str. ToCharArray ();
for (int i=0;i {
if (ch[i]<48 | | ch[i]>57)
return false;
}
return true;
}

b

Copy Code code as follows:

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

Copy Code code as follows:

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;
}

Scheme four: Rewrite the VB isnumeric source code (execution efficiency is not high)

Copy Code code as follows:

Keynote function
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;
}//Child functions
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;
}

Scenario five: Directly referencing VB runtime (inefficient execution)

Method: First you need to add a visualbasic.runtime reference
The using Microsoft.VisualBasic in the code;
The procedure uses Information.isnumeric ("ddddd");

The above is C # to determine whether a string is the entire content of a numeric type, recommend the use of regular expressions of the method , relatively simple and high efficiency.