Convert::ToInt32 Method (String^, Int32)

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

A 32-bit signed integer that is equivalent to the number in value, or 0 (zero) if value is null.

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 ToInt32(String^, Int32) method assumes that negative numbers use two’s complement representation. In other words, the method always interprets the highest-order binary bit of an integer (bit 31) 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 Int32 data type is converted to an Int32 value without the method throwing an exception. The following example increments Int32::MaxValue by one, converts the resulting number to its hexadecimal string representation, and then calls the ToInt32(String^, Int32) method. Instead of throwing an exception, the method displays the message, "0x80000000 converts to -2147483648."

// Create a hexadecimal value out of range of the integer type. 
String^ value1 = Convert::ToString((static_cast<__int64>(int::MaxValue)) + 1, 16);
// Convert it back to a number.
try {
   int number = Convert::ToInt32(value1, 16);
   Console::WriteLine("0x{0} converts to {1}.", value1, number);
}
catch (OverflowException ^e) {
   Console::WriteLine("Unable to convert '0x{0}' to an integer.", value1);
}
// The example displays the following output:
//      0x80000000 converts to -2147483648.

When performing binary operations or numeric conversions, it is always the responsibility of the developer to verify that a method is using 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 retrieving the sign of the numeric value before converting it to its hexadecimal string representation. Throw an exception if the original value was positive but the conversion back to an integer yields a negative value.

__int64 sourceNumber2 = (static_cast<__int64>(int::MaxValue)) + 1;
bool isNegative = Math::Sign(sourceNumber2) == -1;
String^ value2 = Convert::ToString(sourceNumber2, 16);
int targetNumber;
try {
   targetNumber = Convert::ToInt32(value2, 16);
   if (!(isNegative) & (targetNumber & 0x80000000) != 0)
      throw gcnew OverflowException();
   else
      Console::WriteLine("0x{0} converts to {1}.", value2, targetNumber);
}
catch (OverflowException ^e) {
   Console::WriteLine("Unable to convert '0x{0}' to an integer.", value2);
}
// The example displays the following output:
//       Unable to convert '0x80000000' to an integer.