Was this page helpful?
Your feedback about this content is important. Let us know what you think.
Additional feedback?
1500 characters remaining
Export (0) Print
Expand All

Convert::ToByte Method (String, Int32)

Converts the string representation of a number in a specified base to an equivalent 8-bit unsigned integer.

Namespace:  System
Assemblies:   System.Runtime.Extensions (in System.Runtime.Extensions.dll)
  mscorlib (in mscorlib.dll)

public:
static unsigned char ToByte(
	String^ value, 
	int fromBase
)

Parameters

value
Type: System::String

A string that contains the number to convert.

fromBase
Type: System::Int32

The base of the number in value, which must be 2, 8, 10, or 16.

Return Value

Type: System::Byte
An 8-bit unsigned integer that is equivalent to the number in value, or 0 (zero) if value is nullptr.

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.

ArgumentOutOfRangeException

value is String::Empty.

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 base 10 unsigned number, is prefixed with a negative sign.

-or-

value represents a number that is less than Byte::MinValue or greater than Byte::MaxValue.

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

Because the Byte data type supports unsigned values only, the ToByte(String, Int32) method assumes that value is expressed using unsigned binary representation. In other words, all eight 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 byte value that is out of the range of the Byte data type is converted to a Byte value without the method throwing an exception. The following example converts MinValue to its hexadecimal string representation, and then calls the ToByte(String, Int32) method. Instead of throwing an exception, the method displays the message, "0x80 converts to 128."

No code example is currently available or this language may not be supported.

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

No code example is currently available or this language may not be supported.

The following example alternately attempts to interpret an array of strings as the representation of binary, octal, decimal, and hexadecimal values.

No code example is currently available or this language may not be supported.

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

XNA Framework

Supported in: 3.0, 2.0, 1.0

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library
Show:
© 2015 Microsoft