Convert.ToInt64 Method (String, Int32)

 

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)

Public Shared Function ToInt64 (
	value As String,
	fromBase As Integer
) As Long

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.Int64

A 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.

Universal Windows Platform
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
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