Export (0) Print
Expand All

Boolean.TryParse Method

Converts the specified string representation of a logical value to its Boolean equivalent. A return value indicates whether the conversion succeeded or failed.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

public static bool TryParse (
	string value,
	out bool result
)
public static boolean TryParse (
	String value, 
	/** @attribute OutAttribute() */ /** @ref */ boolean result
)
Not applicable.

Parameters

value

A string containing the value to convert.

result

When this method returns, if the conversion succeeded, contains true if value is equivalent to TrueString or false if value is equivalent to FalseString. If the conversion failed, contains false. The conversion fails if value is a null reference (Nothing in Visual Basic) or is not equivalent to either TrueString or FalseString. This parameter is passed uninitialized.

Return Value

true if value was converted successfully; otherwise, false.

The TryParse method is like the Parse method, except the TryParse method does not throw an exception if the conversion fails.

The value parameter can be preceded or followed by white space. The comparison is case-insensitive.

The following code example demonstrates overloads of the TryParse method for several base types, as well as the System.DateTime.TryParseExact method.

// This example demonstrates overloads of the TryParse method for
// several base types, and the TryParseExact method for DateTime.

// In most cases, this example uses the most complex overload; that is, the overload 
// with the most parameters for a particular type. If a complex overload specifies 
// null (Nothing in Visual Basic) for the IFormatProvider parameter, formatting 
// information is obtained from the culture associated with the current thread. 
// If a complex overload specifies the style parameter, the parameter value is 
// the default value used by the equivalent simple overload.

using System;
using System.Globalization;

class Sample 
{
    public static void Main() 
    {
    bool     result;
    CultureInfo ci;
    string   nl = Environment.NewLine;
    string   msg1 = 
             "This example demonstrates overloads of the TryParse method for{0}" +
             "several base types, as well as the TryParseExact method for DateTime.{0}";
    string   msg2 = "Non-numeric types:{0}";
    string   msg3 = "{0}Numeric types:{0}";
    string   msg4 = "{0}The following types are not CLS-compliant:{0}";

// Non-numeric types.
    Boolean  booleanVal;
    Char     charVal;
    DateTime datetimeVal;

// Numeric types.
    Byte     byteVal;
    Int16    int16Val;
    Int32    int32Val;
    Int64    int64Val;
    Decimal  decimalVal;
    Single   singleVal;
    Double   doubleVal;

// The following types are not CLS-compliant.
    SByte    sbyteVal;
    UInt16   uint16Val;
    UInt32   uint32Val;
    UInt64   uint64Val;
//
    Console.WriteLine(msg1, nl);

// Non-numeric types:
    Console.WriteLine(msg2, nl);
// DateTime
  // TryParse:
    // Assume current culture is en-US, and dates of the form: MMDDYYYY.
    result = DateTime.TryParse("7/4/2004 12:34:56", out datetimeVal);
    Show(result, "DateTime #1", datetimeVal.ToString());

    // Use fr-FR culture, and dates of the form: DDMMYYYY.
    ci = new CultureInfo("fr-FR");
    result = DateTime.TryParse("4/7/2004 12:34:56", 
             ci, DateTimeStyles.None, out datetimeVal);
    Show(result, "DateTime #2", datetimeVal.ToString());

  // TryParseExact:
    // Use fr-FR culture. The format, "G", is short date and long time.
    result = DateTime.TryParseExact("04/07/2004 12:34:56", "G", 
             ci, DateTimeStyles.None, out datetimeVal);
    Show(result, "DateTime #3", datetimeVal.ToString());

    // Assume en-US culture.
    string[] dateFormats = {"f", "F", "g", "G"};
    result = DateTime.TryParseExact("7/4/2004 12:34:56 PM", 
             dateFormats, null, DateTimeStyles.None, 
             out datetimeVal);
    Show(result, "DateTime #4", datetimeVal.ToString());

    Console.WriteLine();
// Boolean
    result = Boolean.TryParse("true", out booleanVal);
    Show(result, "Boolean", booleanVal.ToString());
// Char
    result = Char.TryParse("A", out charVal);
    Show(result, "Char", charVal.ToString());

// Numeric types:
    Console.WriteLine(msg3, nl);
// Byte
    result = Byte.TryParse("1", NumberStyles.Integer, null, out byteVal);
    Show(result, "Byte", byteVal.ToString());
// Int16
    result = Int16.TryParse("-2", NumberStyles.Integer, null, out int16Val);
    Show(result, "Int16", int16Val.ToString());
// Int32
    result = Int32.TryParse("3", NumberStyles.Integer, null, out int32Val);
    Show(result, "Int32", int32Val.ToString());
// Int64
    result = Int64.TryParse("4", NumberStyles.Integer, null, out int64Val);
    Show(result, "Int64", int64Val.ToString());
// Decimal
    result = Decimal.TryParse("-5.5", NumberStyles.Number, null, out decimalVal);
    Show(result, "Decimal", decimalVal.ToString());
// Single
    result = Single.TryParse("6.6", 
             (NumberStyles.Float | NumberStyles.AllowThousands), 
             null, out singleVal);
    Show(result, "Single", singleVal.ToString());
// Double
    result = Double.TryParse("-7", 
             (NumberStyles.Float | NumberStyles.AllowThousands), 
             null, out doubleVal);
    Show(result, "Double", doubleVal.ToString());

// Use the simple Double.TryParse overload, but specify an invalid value.

    result = Double.TryParse("abc", out doubleVal);
    Show(result, "Double #2", doubleVal.ToString());
//
    Console.WriteLine(msg4, nl);
// SByte
    result = SByte.TryParse("-8", NumberStyles.Integer, null, out sbyteVal);
    Show(result, "SByte", sbyteVal.ToString());
// UInt16
    result = UInt16.TryParse("9", NumberStyles.Integer, null, out uint16Val);
    Show(result, "UInt16", uint16Val.ToString());
// UInt32
    result = UInt32.TryParse("10", NumberStyles.Integer, null, out uint32Val);
    Show(result, "UInt32", uint32Val.ToString());
// UInt64
    result = UInt64.TryParse("11", NumberStyles.Integer, null, out uint64Val);
    Show(result, "UInt64", uint64Val.ToString());
    }

    protected static void Show(bool parseResult, string typeName, 
                               string parseValue)
    {
    string msgSuccess = "Parse for {0} = {1}";
    string msgFailure = "** Parse for {0} failed. Invalid input.";
//
    if (parseResult == true)
        Console.WriteLine(msgSuccess, typeName, parseValue);
    else
        Console.WriteLine(msgFailure, typeName);
   }
}
/*
This example produces the following results:

This example demonstrates overloads of the TryParse method for
several base types, as well as the TryParseExact method for DateTime.

Non-numeric types:

Parse for DateTime #1 = 7/4/2004 12:34:56 PM
Parse for DateTime #2 = 7/4/2004 12:34:56 PM
Parse for DateTime #3 = 7/4/2004 12:34:56 PM
Parse for DateTime #4 = 7/4/2004 12:34:56 PM

Parse for Boolean = True
Parse for Char = A

Numeric types:

Parse for Byte = 1
Parse for Int16 = -2
Parse for Int32 = 3
Parse for Int64 = 4
Parse for Decimal = -5.5
Parse for Single = 6.6
Parse for Double = -7
** Parse for Double #2 failed. Invalid input.

The following types are not CLS-compliant:

Parse for SByte = -8
Parse for UInt16 = 9
Parse for UInt32 = 10
Parse for UInt64 = 11
*/

// This example demonstrates overloads of the TryParse method for
// several base types, and the TryParseExact method for DateTime.
// In most cases, this example uses the most complex overload; that is, 
// the overload with the most parameters for a particular type. If a 
// complex overload specifies null (Nothing in Visual Basic) for the 
// IFormatProvider parameter, formatting information is obtained from 
// the culture associated with the current thread. If a complex overload 
// specifies the style parameter, the parameter value is the default value 
// used by the equivalent simple overload.

import System.*;
import System.Globalization.*;

class Sample
{
    public static void main(String[] args)
    {
        boolean result;
        CultureInfo ci = null;
        String nl = Environment.get_NewLine();
        String msg1 = "This example demonstrates overloads of the TryParse " 
            + "method for{0}several base types, as well as the TryParseExact " 
            + "method for DateTime.{0}";
        String msg2 = "Non-numeric types:{0}";
        String msg3 = "{0}Numeric types:{0}";
        String msg4 = "{0}The following types are not CLS-compliant:{0}";
        // Non-numeric types.
        System.Boolean booleanVal = (System.Boolean)false;
        System.Char charVal = (System.Char)0;
        DateTime dateTimeVal = System.DateTime.get_Now();
        // Numeric types.
        Byte byteVal = null;
        Int16 int16Val = (Int16)0;
        Int32 int32Val = (Int32)0;
        Int64 int64Val = (Int64)0;
        Decimal decimalVal = new Decimal(0);
        Single singleVal = (Single)0;
        //Double doubleVal = new Double(0);
        double doubleVal = 0;
        // The following types are not CLS-compliant.
        SByte sByteVal = (System.SByte)0;
        UInt16 uInt16Val = (UInt16)0;
        UInt32 uInt32Val = (UInt32)0;
        UInt64 uInt64Val = (UInt64)0;
        //
        Console.WriteLine(msg1, nl);
        // Non-numeric types:
        Console.WriteLine(msg2, nl);
        // DateTime
        // TryParse:
        // Assume current culture is en-US, and dates of the form: MMDDYYYY.
        result = DateTime.TryParse("7/4/2004 12:34:56", dateTimeVal);
        Show(result, "DateTime #1", dateTimeVal.ToString());
        // Use fr-FR culture, and dates of the form: DDMMYYYY.
        ci = new CultureInfo("fr-FR");
        result = DateTime.TryParse("4/7/2004 12:34:56", ci,
            DateTimeStyles.None, dateTimeVal);
        Show(result, "DateTime #2", dateTimeVal.ToString());
        // TryParseExact:
        // Use fr-FR culture. The format, "G", is short date and long time.
        result = DateTime.TryParseExact("04/07/2004 12:34:56", "G", ci, 
            DateTimeStyles.None, dateTimeVal);
        Show(result, "DateTime #3", dateTimeVal.ToString());
        // Assume en-US culture.
        String dateFormats[] =  { "f", "F", "g", "G" };
        result = DateTime.TryParseExact("7/4/2004 12:34:56 PM", dateFormats, 
            null, DateTimeStyles.None, dateTimeVal);
        Show(result, "DateTime #4", dateTimeVal.ToString());

        Console.WriteLine();
        // Boolean
        boolean tempBooleanVal = System.Convert.ToBoolean(booleanVal);
        result = System.Boolean.TryParse("true",/**@out*/ tempBooleanVal);
        Show(result, "Boolean", System.Convert.ToString(tempBooleanVal));
        // Char
        char tempCharVal = System.Convert.ToChar(charVal);
        result = Char.TryParse("A", /**@out*/tempCharVal);
        Show(result, "Char", System.Convert.ToString(tempCharVal));
        // Numeric types:
        Console.WriteLine(msg3, nl);
        // Byte
        ubyte tempByteVal = System.Convert.ToByte(byteVal);
        result = System.Byte.TryParse("1", NumberStyles.Integer, null,
            /**@out*/tempByteVal);
        Show(result, "Byte", System.Convert.ToString(tempByteVal));
        // Int16
        short tempInt16Val = System.Convert.ToInt16(int16Val);
        result = Int16.TryParse("-2", NumberStyles.Integer, null,
            /**@out*/tempInt16Val);
        Show(result, "Int16", System.Convert.ToString(tempInt16Val));
        // Int32
        int tempInt32Val = System.Convert.ToInt32(int32Val);
        result = Int32.TryParse("3", NumberStyles.Integer, null,
            /**@out*/tempInt32Val);
        Show(result, "Int32", System.Convert.ToString(tempInt32Val));
        // Int64
        long tempInt64Val = System.Convert.ToInt64(int64Val);
        result = Int64.TryParse("4", NumberStyles.Integer, null,
            /**@out*/tempInt64Val);
        Show(result, "Int64", System.Convert.ToString(tempInt64Val));
        // Decimal
        result = Decimal.TryParse("-5.5", NumberStyles.Number, null,
            /**@out*/decimalVal);
        Show(result, "Decimal", decimalVal.ToString());
        // Single
        float tempSingleVal = System.Convert.ToSingle(singleVal);
        result = Single.TryParse("6.6", NumberStyles.Float 
            | NumberStyles.AllowThousands, null, /**@out*/tempSingleVal);
        Show(result, "Single", System.Convert.ToString(tempSingleVal));
        // Double
        result = System.Double.TryParse("-7", NumberStyles.Float 
            | NumberStyles.AllowThousands, null, /**@out*/doubleVal);
        Show(result, "Double", System.Convert.ToString(doubleVal));
        // Use the simple Double.TryParse overload, but specify an invalid value.
        result = System.Double.TryParse("abc", doubleVal);
        Show(result, "Double #2", System.Convert.ToString(doubleVal));
        //
        Console.WriteLine(msg4, nl);
        // SByte
        byte tempSByteVal = System.Convert.ToSByte(sByteVal);
        result = SByte.TryParse("-8", NumberStyles.Integer, null,
            /**@out*/tempSByteVal);
        Show(result, "SByte", System.Convert.ToString(tempSByteVal));
        // UInt16
        result = UInt16.TryParse("9", NumberStyles.Integer, null,
            /**@out*/uInt16Val);
        Show(result, "UInt16", uInt16Val.ToString());
        // UInt32
        result = UInt32.TryParse("10", NumberStyles.Integer, null,
            /**@out*/uInt32Val);
        Show(result, "UInt32", uInt32Val.ToString());
        // UInt64
        result = UInt64.TryParse("11", NumberStyles.Integer, null,
            /**@out*/uInt64Val);
        Show(result, "UInt64", uInt64Val.ToString());
    } //main

    protected static void Show(boolean parseResult,
        String typeName, String parseValue)
    {
        String msgSuccess = "Parse for {0} = {1}";
        String msgFailure = "** Parse for {0} failed. Invalid input.";
        //
        if (parseResult == true) {
            Console.WriteLine(msgSuccess, typeName, parseValue);
        }
        else {
            Console.WriteLine(msgFailure, typeName);
        }
    } //Show
} //Sample 
 /*
This example produces the following results:

This example demonstrates overloads of the TryParse method for
several base types, as well as the TryParseExact method for DateTime.

Non-numeric types:

Parse for DateTime #1 = 7/4/2004 12:34:56 PM
Parse for DateTime #2 = 7/4/2004 12:34:56 PM
Parse for DateTime #3 = 7/4/2004 12:34:56 PM
Parse for DateTime #4 = 7/4/2004 12:34:56 PM

Parse for Boolean = True
Parse for Char = A

Numeric types:

Parse for Byte = 1
Parse for Int16 = -2
Parse for Int32 = 3
Parse for Int64 = 4
Parse for Decimal = -5.5
Parse for Single = 6.6
Parse for Double = -7
** Parse for Double #2 failed. Invalid input.

The following types are not CLS-compliant:

Parse for SByte = -8
Parse for UInt16 = 9
Parse for UInt32 = 10
Parse for UInt64 = 11
*/

Windows 98, Windows Server 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

Community Additions

ADD
Show:
© 2014 Microsoft