Export (0) Print
Expand All
This topic has not yet been rated - Rate this topic

Convert.ToUInt64 Method (String, Int32)

Converts the string representation of a number in a specified base to an equivalent 64-bit unsigned integer.

This API is not CLS-compliant. 

Namespace:  System
Assembly:  mscorlib (in mscorlib.dll)
[CLSCompliantAttribute(false)]
public static ulong ToUInt64(
	string value,
	int fromBase
)

Parameters

value
Type: System.String
A string containing a number.
fromBase
Type: System.Int32
The base of the number in value, which must be 2, 8, 10, or 16.

Return Value

Type: System.UInt64
A 64-bit unsigned integer equivalent to the number in value.
-or-
Zero if value is null.
ExceptionCondition
ArgumentException

fromBase is not 2, 8, 10, or 16.

-or-

value, which represents a non-base 10 unsigned number, is prefixed with a negative sign.

FormatException

value contains a character that is not a valid digit in the base specified by fromBase. The exception message indicates that there are no digits to convert if the first character in value is invalid; otherwise, the message indicates that value contains invalid trailing characters.

OverflowException

value, which represents a non-base 10 unsigned number, is prefixed with a negative sign.

-or-

The return value is less than UInt64.MinValue or larger than UInt64.MaxValue.

If fromBase is 16, you can prefix the number specified by the value parameter with "0x" or "0X".

Because the UInt64 data type supports unsigned values only, the ToUInt64(String, Int32) method assumes that value is expressed using unsigned binary representation. In other words, all 64 bits are used to represent the numeric value and a sign bit is absent. As a result, it is possible to write code in which a signed long integer value that is out of the range of the UInt64 data type is converted to a UInt64 value without the method throwing an exception. The following example converts MinValue to its hexadecimal string representation and then calls the ToUInt64(String, Int32) method. Rather than throwing an exception, the method displays the message, "0x8000000000000000 converts to 9223372036854775808."


// Create a hexadecimal value out of range of the UInt64 type.
string value = Convert.ToString(Int64.MinValue, 16);
// Convert it back to a number.
try
{
   UInt64 number = Convert.ToUInt64(value, 16);
   outputBlock.Text += String.Format("0x{0} converts to {1}.", value, number) + "\n";
}
catch (OverflowException)
{
   outputBlock.Text += String.Format("Unable to convert '0x{0}' to an unsigned long integer.",
                     value) + "\n";
}


When performing binary operations or numeric conversions, it is always the responsibility of the developer to verify that a method or operator uses the appropriate numeric representation to interpret a particular value. The following example illustrates one technique for ensuring that the method does not inappropriately use binary representation to interpret a value that uses two's complement representation when converting a hexadecimal string to a UInt64 value. It determines whether a value represents a signed or an unsigned integer at the same time that it converts that value to its string representation. When converting the value to a UInt64 value, the example checks whether the original value was a signed integer. If so, and its high-order bit is set (which indicates that the original value was negative), the method throws an exception.


// Create a negative hexadecimal value out of range of the UInt64 type.
long sourceNumber = Int64.MinValue;
bool isSigned = Math.Sign((long)sourceNumber.GetType().GetField("MinValue").GetValue(null)) == -1;
string value = Convert.ToString(sourceNumber, 16);
UInt64 targetNumber;
try
{
   targetNumber = Convert.ToUInt64(value, 16);
   if (isSigned && ((targetNumber & 0x8000000000000000) != 0))
      throw new OverflowException();
   else
      outputBlock.Text += String.Format("0x{0} converts to {1}.", value, targetNumber) + "\n";
}
catch (OverflowException)
{
   outputBlock.Text += String.Format("Unable to convert '0x{0}' to an unsigned long integer.",
                     value) + "\n";
}
// Displays the following:
//    Unable to convert '0x8000000000000000' to an unsigned long integer.     


Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

Did you find this helpful?
(1500 characters remaining)
Thank you for your feedback

Community Additions

ADD
Show:
© 2014 Microsoft. All rights reserved.