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Convert.ToSByte Method (String, Int32)

Silverlight

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

This API is not CLS-compliant.

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

[CLSCompliantAttribute(false)]
public static sbyte ToSByte(
	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.SByte
An 8-bit signed integer equivalent to the number in value.
-or-
Zero if value is null.

Exceptions

Exception	Condition
ArgumentException	fromBase is not 2, 8, 10, or 16. -or- value, which represents a non-base 10 signed 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 signed number, is prefixed with a negative sign. -or- The return value is less than SByte.MinValue or larger than SByte.MaxValue.

Exception

Condition

ArgumentException

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

-or-

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

-or-

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

Remarks

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

Because the negative sign is not supported for non-base 10 numeric representations, the ToSByte(String, Int32) method assumes that negative numbers use two’s complement representation. In other words, the method always interprets the high-order bit of a byte (bit 7) as its sign bit. As a result, it is possible to write code in which a non-base 10 number that is out of the range of the SByte data type is converted to an SByte value without the method throwing an exception. The following example converts MaxValue to its hexadecimal string representation and then calls the ToSByte(String, Int32) method. Rather than throwing an exception, the method displays the message, " 0xff converts to -1."


// Create a hexadecimal value out of range of the SByte type.
string value = Convert.ToString(byte.MaxValue, 16);
// Convert it back to a number.
try
{
   sbyte number = Convert.ToSByte(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 a signed byte.", value) + "\n";
}

When performing binary operations or numeric conversions, it is always the responsibility of the developer to verify that a method uses the appropriate numeric representation to interpret a particular value. As the following example illustrates, you can ensure that the method handles overflows appropriately by first determining whether a value represents an unsigned or a signed type when converting it to its hexadecimal string representation. Then, throw an exception if the conversion back to a signed byte yields a value whose sign bit is on but whose original value was an unsigned type.


// Create a hexadecimal value out of range of the SByte type.
byte sourceNumber = byte.MaxValue;
bool isSigned = Math.Sign(Convert.ToDouble(sourceNumber.GetType().GetField("MinValue").GetValue(null))) == -1;
string value = Convert.ToString(sourceNumber, 16);
sbyte targetNumber;
try
{
   targetNumber = Convert.ToSByte(value, 16);
   if (!isSigned && ((targetNumber & 0x80) != 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 a signed byte.", value) + "\n";
}
// Displays the following:
//    Unable to convert '0xff' to a signed byte.