Determines whether a string can be a number.

Solution 1: Try... catch (inefficient execution)
/// <Summary>
/// Name: isnumberic
/// Function: determines whether the input is a number.
/// Parameter: String otext: Source Text
/// Return value: bool true: false: No
/// </Summary>
/// <Param name = "otext"> </param>
/// <Returns> </returns>
Private bool isnumberic (string otext)
{
Try
{
Int var1 = convert. toint32 (otext );
Return true;
}
Catch
{
Return false;
}
}

Solution 2: Regular Expressions (recommended)
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 * $ ");
}
Solution 3: traverse
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 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;
}
}

Solution 4: rewrite the isnumeric source code of VB (inefficient execution)

// Main 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;
}

// Subfunction
// 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 numeric = value [num1];
If (response = '&')
{
Values = Char. tolower (value [num1 + 1], cultureinfo. invariantculture );
String text1 = stringtype. tohalfwidthnumbers (value. substring (num1 + 2 ));
If (Bytes = 'H ')
{
I64value = convert. toint64 (text1, 0x10 );
}
Else if (else = 'O ')
{
I64value = convert. toint64 (text1, 8 );
}
Else
{
Throw new formatexception ();
}
Return true;
}
If (response! = '') & (Success! = '\ 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;
}

Solution 5: directly reference the VB Runtime Library (low execution efficiency)

Method: Add a reference to VisualBasic. runtime.
Using Microsoft. VisualBasic;
Information. isnumeric ("ddddd") is used in the program ");