共用方式為


SqlRoleProvider.RoleExists(String) 方法

定義

取得值,指出指定的角色名稱是否已存在於角色資料庫中。

public:
 override bool RoleExists(System::String ^ roleName);
public override bool RoleExists (string roleName);
override this.RoleExists : string -> bool
Public Overrides Function RoleExists (roleName As String) As Boolean

參數

roleName
String

要在資料庫中搜尋的角色名稱。

傳回

如果角色名稱已存在於資料庫中,則為 true,否則為 false

例外狀況

roleNamenull

roleName 是空字串,或包含逗號。

-或-

roleName 的長度超過 256 個字元。

與資料庫通訊時發生未知的錯誤。

範例

下列程式代碼範例會 RoleExists 使用 方法來判斷角色名稱是否已經存在,再建立角色。 如需啟用角色管理的 Web.config 檔案範例,請參閱 SqlRoleProvider

重要

此範例包含一個文本框,可接受用戶輸入,這是潛在的安全性威脅。 根據預設,ASP.NET Web 網頁會驗證使用者輸入未包含指令碼或 HTML 項目。 如需詳細資訊,請參閱 Script Exploits Overview (指令碼攻擊概觀)。

<%@ Page Language="C#" %>
<%@ 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">

string[] rolesArray;

public void Page_Load(object sender, EventArgs args)
{
  if (!IsPostBack)
  {
    // Bind roles to GridView.

    rolesArray = Roles.GetAllRoles();
    RolesGrid.DataSource = rolesArray;
    RolesGrid.DataBind();
  }
}

public void CreateRole_OnClick(object sender, EventArgs args)
{
  string createRole = RoleTextBox.Text;

  try
  {
    if (Roles.RoleExists(createRole))
    {
      Msg.Text = "Role '" + Server.HtmlEncode(createRole) + "' already exists. Please specify a different role name.";
      return;
    }

    Roles.CreateRole(createRole);

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

    // Re-bind roles to GridView.

    rolesArray = Roles.GetAllRoles();
    RolesGrid.DataSource = rolesArray;
    RolesGrid.DataBind();
  }
  catch (Exception e)
  {
    Msg.Text = "Role '" + Server.HtmlEncode(createRole) + "' <u>not</u> created.";
    Response.Write(e.ToString());
  }

}

</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>
<%@ 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>

備註

類別 RoleExistsRoles 呼叫 方法,以判斷角色名稱是否存在於 ASP.NET 應用程式組態檔中指定的 SQL Server 資料庫中 (Web.config) 。

適用於

另請參閱