RoleProvider.RoleExists(String) 方法

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

参数

返回

如果配置后的 applicationName 的数据源中已存在角色名，则为 true；否则为 false。

示例

下面的代码示例演示 了 方法的示例 RoleExists 实现。

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

注解

RoleExists 由 RoleExists 类的 Roles 方法调用，以确定所配置的 ApplicationName的数据源中是否存在角色名称。

如果指定的角色名称为 null 或 为空字符串，建议提供程序引发异常。

另请参阅

• 实现角色提供程序