Roles.RoleExists Method

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

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

'Declaration
Public Shared Function RoleExists ( _
	roleName As String _
) As Boolean
'Usage
Dim roleName As String
Dim returnValue As Boolean

returnValue = Roles.RoleExists(roleName)
public static boolean RoleExists (
	String roleName
)
public static function RoleExists (
	roleName : String
) : boolean
Not applicable.

Parameters

roleName

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

Return Value

true if the role name already exists in the data source; otherwise, false.

Exception typeCondition

System.ArgumentNullException

roleName is a null reference (Nothing in Visual Basic) (Nothing in Visual Basic).

System.ArgumentException

roleName is an empty string or contains a comma (,).

System.Configuration.Provider.ProviderException

Role management is not enabled.

The RoleExists method calls the RoleExists method of the default role provider to determine whether a role name exists in the data source for the application that is specified in the ApplicationName property.

The following code example uses the RoleExists method to determine whether a role name already exists before creating the role. For an example of a Web.config file that enables role management, see Roles.

Security noteSecurity Note:

This example contains a text box that accepts user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview (Visual Studio).

<%@ Page Language="VB" %>
<%@ Import Namespace="System.Web.Security" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

Dim rolesArray() As String

Public Sub Page_Load(sender As Object, args As EventArgs)

  If Not IsPostBack Then
    ' Bind roles to GridView.

    rolesArray = Roles.GetAllRoles()
    RolesGrid.DataSource = rolesArray
    RolesGrid.DataBind()
  End If

End Sub

Public Sub CreateRole_OnClick(sender As Object, args As EventArgs)

  Dim createRole As String = RoleTextBox.Text

  Try
    If Roles.RoleExists(createRole) Then
      Msg.Text = "Role '" & Server.HtmlEncode(createRole) & "' already exists. Please specify a different role name."
      Return
    End If

    Roles.CreateRole(createRole)

    Msg.Text = "Role '" & Server.HtmlEncode(createRole) & "' created."

    ' Re-bind roles to GridView.

    rolesArray = Roles.GetAllRoles()
    RolesGrid.DataSource = rolesArray
    RolesGrid.DataBind()
  Catch
    Msg.Text = "Role '" & Server.HtmlEncode(createRole) & "' <u>not</u> created."
  End Try

End Sub

</script>
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
<title>Sample: Create Role</title>
</head>
<body>

<form runat="server" id="PageForm">
  <h3>Create a Role</h3>

  <asp:Label id="Msg" ForeColor="maroon" runat="server" /><br />

  Role name: 

  <asp:TextBox id="RoleTextBox" runat="server" />

  <asp:Button Text="Create Role" id="CreateRoleButton"
              runat="server" OnClick="CreateRole_OnClick" />

  <br />

  <asp:GridView runat="server" CellPadding="2" id="RolesGrid" 
                Gridlines="Both" CellSpacing="2" AutoGenerateColumns="false" >
    <HeaderStyle BackColor="navy" ForeColor="white" />
    <Columns>
      <asp:TemplateField HeaderText="Roles" >
        <ItemTemplate>
          <%# Container.DataItem.ToString() %>
        </ItemTemplate>
      </asp:TemplateField>
    </Columns>
   </asp:GridView>
</form>

</body>
</html>

Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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