Convert.ToInt64 Method (String, Int32)
Converts the string representation of a number in a specified base to an equivalent 64-bit signed integer.
Assembly: mscorlib (in mscorlib.dll)
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.Int64A 64-bit signed integer that is equivalent to the number in value, or 0 (zero) if value is null.
| 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. |
| ArgumentOutOfRangeException | value is String.Empty. |
| 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 Int64.MinValue or greater than Int64.MaxValue. |
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. Instead of 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) Console.WriteLine("0x{0} converts to {1}.", value, number) Catch e As OverflowException Console.WriteLine("Unable to convert '0x{0}' to a long integer.", value) End Try
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 determining whether a value represents an unsigned or a signed type when converting it to its hexadecimal string representation. Throw an exception if the original value was an unsigned type but the conversion back to an integer yields a value whose sign bit is on.
' Create a negative hexadecimal value out of range of the Long type. Dim sourceNumber As ULong = ULong.MaxValue Dim isSigned As Boolean = Math.Sign(sourceNumber.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 Console.WriteLine("0x{0} converts to {1}.", value, targetNumber) End If Catch e As OverflowException Console.WriteLine("Unable to convert '0x{0}' to a long integer.", value) End Try ' Displays the following to the console: ' Unable to convert '0xFFFFFFFFFFFFFFFF' to a long integer.
The following example attempts to interpret each element in a string array as a hexadecimal string and convert it to a long integer.
Module Example Public Sub Main() Dim hexStrings() As String = { "8000000000000000", "0FFFFFFFFFFFFFFF", _ "f0000000000001000", "00A30", "D", "-13", "GAD" } For Each hexString As String In hexStrings Try Dim number As Long = Convert.ToInt64(hexString, 16) Console.WriteLine("Converted '{0}' to {1:N0}.", hexString, number) Catch e As FormatException Console.WriteLine("'{0}' is not in the correct format for a hexadecimal number.", _ hexString) Catch e As OverflowException Console.WriteLine("'{0}' is outside the range of an Int64.", hexString) Catch e As ArgumentException Console.WriteLine("'{0}' is invalid in base 16.", hexString) End Try Next End Sub End Module ' The example displays the following output: ' Converted '8000000000000000' to -9,223,372,036,854,775,808. ' Converted '0FFFFFFFFFFFFFFF' to 1,152,921,504,606,846,975. ' 'f0000000000001000' is outside the range of an Int64. ' Converted '00A30' to 2,608. ' Converted 'D' to 13. ' '-13' is invalid in base 16. ' 'GAD' is not in the correct format for a hexadecimal number.
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1