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BigInteger Explicit Conversion (BigInteger to UInt64)

Defines an explicit conversion of a BigInteger object to an unsigned 64-bit integer value.

This API is not CLS-compliant. The CLS-compliant alternative is .

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

public static explicit operator ulong (
	BigInteger value


Type: System.Numerics.BigInteger
The value to convert to an unsigned 64-bit integer.

Return Value

Type: System.UInt64
An object that contains the value of the value parameter.


value is less than UInt64.MinValue.


value is greater than UInt64.MaxValue.

The overloads of the Explicit(Decimal to BigInteger) method define the types to which or from which a BigInteger object can be converted. Language compilers do not perform this conversion automatically because it can involve data loss. Instead, they perform the conversion only if a casting operator (in C#) or a conversion function (such as CType or CULng in Visual Basic) is used. Otherwise, they display a compiler error.

Because this operation defines a narrowing conversion, it can throw an OverflowException at run time if the BigInteger value is outside the range of the UInt64 data type. There is no loss of precision in the resulting UInt64 value if the conversion is successful.

The following example illustrates the conversion of BigInteger values to UInt64 values. It also handles an OverflowException that is thrown because the BigInteger value is outside the range of the UInt64 data type.

// BigInteger to UInt64 conversion.
BigInteger goodULong = 2000000000;
BigInteger badULong = BigInteger.Pow(goodULong, 3);

ulong uLongFromBigInteger;

// Successful conversion using cast operator. 
uLongFromBigInteger = (ulong) goodULong;

// Handle conversion that should result in overflow.
   uLongFromBigInteger = (ulong) badULong;
catch (OverflowException e)
   Console.WriteLine("Unable to convert {0}:\n   {1}", 
                     badULong, e.Message);

.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.