Public Function BeginExecuteReader(
     ByVal callback As AsyncCallback,
    ByVal stateObject As Object,
    ByVal cmdBehavior As CommandBehavior
) As IAsyncResult

public IAsyncResult BeginExecuteReader(
     AsyncCallback callback,
    object stateObject,
    CommandBehavior cmdBehavior
)

可只用于进行轮询、只用于等待结果或返回轮询和等待结果这两者的 System.IAsyncResult；调用 EndExecuteReader(IAsyncResult) 方法（返回可用于检索返回行的 ULDataReader 对象）时也需要此值。

• ULCommand.EndExecuteReader 方法 [UltraLite.NET]
• ULDataReader 类 [UltraLite.NET]
•  System.AsyncCallback
•  System.IAsyncResult
•  System.IAsyncResult.AsyncState
•  System.Data.CommandBehavior
•  System.Data.CommandBehavior.Default
•  System.Data.CommandBehavior.CloseConnection
•  System.Data.CommandBehavior.SchemaOnly