Convert.ToInt32 Method (String, Int32)
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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
'Declaration
Public Shared Function ToInt32 ( _
value As String, _
fromBase As Integer _
) As Integer
public static int ToInt32(
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.Int32
A 32-bit signed integer equivalent to the number in value.
-or-
Zero if value is nulla 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- The return value is less than Int32.MinValue or larger 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. Rather than throwing an exception, the method displays the message, "0x80000000 converts to -2147483648."
' 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)
outputBlock.Text += String.Format("0x{0} converts to {1}.", value, number) & vbCrLf
Catch e As OverflowException
outputBlock.Text += String.Format("Unable to convert '0x{0}' to an integer.", value) & vbCrLf
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);
outputBlock.Text += String.Format("0x{0} converts to {1}.", value, number.ToString()) + "\n";
}
catch (OverflowException)
{
outputBlock.Text += String.Format("Unable to convert '0x{0}' to an integer.", 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 retrieving the sign of the numeric value before converting it to its hexadecimal string representation. Then throw an exception if the conversion back to an integer yields a negative value when the original value was positive.
' 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
outputBlock.Text += String.Format("0x{0} converts to {1}.", value, targetNumber) & vbCrLf
End If
Catch e As OverflowException
outputBlock.Text += String.Format("Unable to convert '0x{0}' to an integer.", value) & vbCrLf
End Try
' Displays the following:
' 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
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 integer.", value) + "\n";
}
// Displays the following:
// Unable to convert '80000000' to an integer.
Version Information
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
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.