語言

RoleProvider.RoleExists(String) 方法

定義

命名空間:
System.Web.Security
組件:
System.Web.dll
組件:
System.Web.ApplicationServices.dll

會獲得一個值，表示指定的角色名稱是否已存在於已配置 applicationName的角色資料來源中。

public:
 abstract bool RoleExists(System::String ^ roleName);
public abstract bool RoleExists(string roleName);
abstract member RoleExists : string -> bool
Public MustOverride Function RoleExists (roleName As String) As Boolean

參數

roleName
String

要在資料來源中搜尋的職缺名稱。

傳回

Boolean

true若角色名稱已存在於配置applicationName的資料來源中;否則， false

範例

以下程式碼範例展示了該 RoleExists 方法的範例實作。

public override bool RoleExists(string rolename)
{
  if (rolename == null || rolename == "")
    throw new ProviderException("Role name cannot be empty or null.");

  bool exists = false;

  OdbcConnection conn = new OdbcConnection(connectionString);
  OdbcCommand cmd = 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();

    int numRecs = (int)cmd.ExecuteScalar();

    if (numRecs > 0)
    {
      exists = true;
    }
  }
  catch (OdbcException)
  {
    // Handle exception.
  }
  finally
  {
    conn.Close();      
  }

  return exists;
}

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

備註

RoleExists 是透過 RoleExists 類別的方法 Roles 來判斷配置 ApplicationName的 。

如果指定的角色名稱是 null 空字串，我們建議你的提供者拋出例外。

適用於

另請參閱