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RoleProvider.RoleExists Method

Gets a value indicating whether the specified role name already exists in the role data source for the configured applicationName.

Namespace:  System.Web.Security
Assembly:  System.Web (in System.Web.dll)

'Declaration
Public MustOverride Function RoleExists ( _
	roleName As String _
) As Boolean
'Usage
Dim instance As RoleProvider 
Dim roleName As String 
Dim returnValue As Boolean 

returnValue = instance.RoleExists(roleName)

Parameters

roleName
Type: System.String

The name of the role to search for in the data source.

Return Value

Type: System.Boolean
true if the role name already exists in the data source for the configured applicationName; otherwise, false.

RoleExists is called by the RoleExists method of the Roles class to determine whether a role name exists in the data source for the configured ApplicationName.

If the specified role name is Nothing or is an empty string, we recommend that your provider throw an exception.

The following code example shows a sample implementation of the RoleExists method.

Public Overrides Function RoleExists(ByVal rolename As String) As Boolean 

    If rolename Is Nothing OrElse rolename = "" Then _
      Throw New ProviderException("Role name cannot be empty or null.")

    Dim exists As Boolean = False 

    Dim conn As OdbcConnection = New OdbcConnection(connectionString)
    Dim cmd As OdbcCommand = New OdbcCommand("SELECT COUNT(*) FROM Roles " & _
                                             " WHERE Rolename = ? AND ApplicationName = ?", conn)

    cmd.Parameters.Add("@Rolename", OdbcType.VarChar, 255).Value = rolename
    cmd.Parameters.Add("@ApplicationName", OdbcType.VarChar, 255).Value = ApplicationName

    Try
        conn.Open()

        Dim numRecs As Integer = CType(cmd.ExecuteScalar(), Integer)

        If numRecs > 0 Then
            exists = True 
        End If 
    Catch e As OdbcException
        ' Handle exception. 
    Finally
        conn.Close()
    End Try 

    Return exists
End Function

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0
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