Convert.ToInt64 Method (String, Int32)
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Converts the string representation of a number in a specified base to an equivalent 64-bit signed integer.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Shared Function ToInt64 ( _
value As String, _
fromBase As Integer _
) As Long
public static long ToInt64(
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.Int64
A 64-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 Int64.MinValue or larger than Int64.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 ToInt64(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 a long integer (bit 63) 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 Int64 data type is converted to an Int64 value without the method throwing an exception. The following example converts MaxValue to its hexadecimal string representation and then calls the ToInt64(String, Int32) method. Rather than throwing an exception, the method displays the message, "0xFFFFFFFFFFFFFFFF converts to -1."
' Create a hexadecimal value out of range of the Long type.
Dim value As String = ULong.MaxValue.ToString("X")
' Call Convert.ToInt64 to convert it back to a number.
Try
Dim number As Long = Convert.ToInt64(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 a long integer.", value) & vbCrLf
End Try
// Create a hexadecimal value out of range of the long type.
string value = ulong.MaxValue.ToString("X");
// Use Convert.ToInt64 to convert it back to a number.
try
{
long number = Convert.ToInt64(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 long 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 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 an integer yields a value whose sign bit is on but whose original value was an unsigned type.
' Create a negative hexadecimal value out of range of the Long type.
Dim sourceNumber As ULong = ULong.MaxValue
Dim isSigned As Boolean = Math.Sign(ULong.MinValue) = -1
Dim value As String = sourceNumber.ToString("X")
Dim targetNumber As Long
Try
targetNumber = Convert.ToInt64(value, 16)
If Not isSigned And ((targetNumber And &H8000000000) <> 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 a long integer.", value) & vbCrLf
End Try
' Displays the following:
' Unable to convert '0xFFFFFFFFFFFFFFFF' to a long integer.
// Create a negative hexadecimal value out of range of the Byte type.
ulong sourceNumber = ulong.MaxValue;
bool isSigned = Math.Sign(Convert.ToDouble(sourceNumber.GetType().GetField("MinValue").GetValue(null))) == -1;
string value = sourceNumber.ToString("X");
long targetNumber;
try
{
targetNumber = Convert.ToInt64(value, 16);
if (!isSigned && ((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 a long integer.", value) + "\n";
}
// Displays the following:
// Unable to convert '0xFFFFFFFFFFFFFFFF' to a long 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.