Convert.ToInt32 Method (String, Int32) (System)

ToInt32 Method (String, Int32)

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework Class Library

Convert..::.ToInt32 Method (String, Int32)

Converts the string representation of a number in a specified base to an equivalent 32-bit signed integer.

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

Syntax

Visual Basic (Declaration)

Public Shared Function ToInt32 ( _
    value As String, _
    fromBase As Integer _
) As Integer

Visual Basic (Usage)

Dim value As String
Dim fromBase As Integer
Dim returnValue As Integer

returnValue = Convert.ToInt32(value, _
    fromBase)

public static int ToInt32(
    string value,
    int fromBase
)

Visual C++

public:
static int ToInt32(
    String^ value, 
    int fromBase
)

JScript

public static function ToInt32(
    value : String, 
    fromBase : int
) : int

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..::.Int32
A 32-bit signed integer that is equivalent to the number in value, or 0 (zero) if value is nullNothingnullptra null reference (Nothing in Visual Basic).

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- value represents a number that is less than Int32..::.MinValue or greater than Int32..::.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-

value represents a number that is less than Int32..::.MinValue or greater than Int32..::.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 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."

Visual Basic

' Create a hexadecimal value out of range of the Integer type.
Dim value As String = Convert.ToString(CLng(Integer.MaxValue) + 1, 16)
' Convert it back to a number.
Try
   Dim number As Integer = Convert.ToInt32(value, 16)
   Console.WriteLine("0x{0} converts to {1}.", value, number)
Catch e As OverflowException
   Console.WriteLine("Unable to convert '0x{0}' to an integer.", value)
End Try

// Create a hexadecimal value out of range of the Integer type.
string value = Convert.ToString((long) int.MaxValue + 1, 16);
// Convert it back to a number.
try
{
   int number = Convert.ToInt32(value, 16);
   Console.WriteLine("0x{0} converts to {1}.", value, number.ToString());
}
catch (OverflowException)
{
   Console.WriteLine("Unable to convert '0x{0}' to an integer.", value);
}

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.

Visual Basic

' Create a hexadecimal value out of range of the Integer type.
Dim sourceNumber As Long = CLng(Integer.MaxValue) + 1
Dim isNegative As Boolean = (Math.Sign(sourceNumber) = -1)
Dim value As String = Convert.ToString(sourceNumber, 16)
Dim targetNumber As Integer
Try
   targetNumber = Convert.ToInt32(value, 16)
   If Not isNegative And ((targetNumber And &H80000000) <> 0) Then
      Throw New OverflowException()
   Else 
      Console.WriteLine("0x{0} converts to {1}.", value, targetNumber)
   End If    
Catch e As OverflowException
   Console.WriteLine("Unable to convert '0x{0}' to an integer.", value)
End Try 
' Displays the following to the console:
'    Unable to convert '0x80000000' to an integer.

// Create a hexadecimal value out of range of the Integer type.
long sourceNumber = (long) int.MaxValue + 1;
bool isNegative = Math.Sign(sourceNumber) == -1;
string value = Convert.ToString(sourceNumber, 16);
int targetNumber;
try
{
   targetNumber = Convert.ToInt32(value, 16);
   if (!(isNegative) & (targetNumber & 0x80000000) != 0) 
      throw new OverflowException();
   else 
      Console.WriteLine("0x{0} converts to {1}.", value, targetNumber);
}
catch (OverflowException)
{
   Console.WriteLine("Unable to convert '0x{0}' to an integer.", value);
} 
// Displays the following to the console:
//    Unable to convert '80000000' to an integer.

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

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

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

Reference