TryParse(TEnum) Method (String, Boolean, TEnum)

Enum.TryParse(Of TEnum) Method (String, Boolean, TEnum)

.NET Framework (current version)
 

Converts the string representation of the name or numeric value of one or more enumerated constants to an equivalent enumerated object. A parameter specifies whether the operation is case-sensitive. The return value indicates whether the conversion succeeded.

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

Public Shared Function TryParse(Of TEnum As Structure) (
	value As String,
	ignoreCase As Boolean,
	<OutAttribute> ByRef result As TEnum
) As Boolean

Parameters

value
Type: System.String

The string representation of the enumeration name or underlying value to convert.

ignoreCase
Type: System.Boolean

true to ignore case; false to consider case.

result
Type: TEnum

When this method returns, result contains an object of type TEnum whose value is represented by value if the parse operation succeeds. If the parse operation fails, result contains the default value of the underlying type of TEnum. Note that this value need not be a member of the TEnum enumeration. This parameter is passed uninitialized.

Return Value

Type: System.Boolean

true if the value parameter was converted successfully; otherwise, false.

Type Parameters

TEnum

The enumeration type to which to convert value.

Exception Condition
ArgumentException

TEnum is not an enumeration type.

TryParse(Of TEnum)(String, Boolean, TEnum) is identical to the Parse(Type, String, Boolean) method, except that instead of throwing an exception, it returns false if the conversion fails. It eliminates the need for exception handling when parsing the string representation of an enumeration value.

The value parameter contains the string representation of an enumeration member's underlying value or named constant, or a list of named constants or underlying values delimited by commas (,). If value includes multiple named constants or values, one or more blank spaces can precede or follow each value, name, or comma in value. If value is a list, result reflects the value of the specified names or underlying values combined with a bitwise OR operation. If value is the string representation of the name of an enumeration value, the comparison of value with enumeration names depends on the ignoreCase parameter. If true, the comparison is case-insensitive; if false, it is case-sensitive.

If value is a name that does not correspond to a named constant of TEnum, the method returns false. If value is the string representation of an integer that does not represent an underlying value of the TEnum enumeration, the method returns an enumeration member whose underlying value is value converted to an integral type. If this behavior is undesirable, call the IsDefined method to ensure that a particular string representation of an integer is actually a member of TEnum.

The following example defines a Colors enumeration, calls the TryParse(Of TEnum)(String, Boolean, TEnum) method to convert strings to their corresponding enumeration values, and calls the IsDefined method to ensure that particular integral values are underlying values in the Colors enumeration. The TryParse(Of TEnum)(String, Boolean, TEnum) method uses case-insensitive comparison when trying to convert the string representations of named constants to their equivalent enumeration values.

<Flags> Enum Colors As Integer
   None = 0
   Red = 1
   Green = 2
   Blue = 4
End Enum

Module Example
   Public Sub Main()
      Dim colorStrings() As String = {"0", "2", "8", "blue", "Blue", "Yellow", "Red, Green"}
      For Each colorString As String In colorStrings
         Dim colorValue As Colors
         If [Enum].TryParse(colorString, True, colorValue) Then        
            If [Enum].IsDefined(GetType(Colors), colorValue) Or colorValue.ToString().Contains(",") Then 
               Console.WriteLine("Converted '{0}' to {1}.", colorString, colorValue.ToString())
            Else
               Console.WriteLine("{0} is not an underlying value of the Colors enumeration.", colorString)            
            End If                    
         Else
            Console.WriteLine("{0} is not a member of the Colors enumeration.", colorString)
         End If
      Next
   End Sub
End Module
' The example displays the following output:
'       Converted '0' to None.
'       Converted '2' to Green.
'       8 is not an underlying value of the Colors enumeration.
'       Converted 'blue' to Blue.
'       Converted 'Blue' to Blue.
'       Yellow is not a member of the Colors enumeration.
'       Converted 'Red, Green' to Red, Green.

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 4.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
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