问题描述
System.Data.SqlClient.SqlCommand有方法
System.Data.SqlClient.SqlCommandhas methods
BeginExecuteNonQuery
BeginExecuteReader
BeginExecuteXmlReader
和
EndExecuteNonQuery
EndExecuteReader
EndExecuteXmlReader
用于异步执行.
System.Data.IDbCommand只有
System.Data.IDbCommandonly has
ExecuteNonQuery
ExecuteReader
ExecuteXmlReader
仅用于同步操作.
是否有用于异步操作的接口?
另外，为什么没有BeginExecuteScalar?
Is there any interface for asynchronous operations ?
In addition, why is there no BeginExecuteScalar ?
推荐答案
IDbCommand不具有begin/end异步方法，因为在ADO.NET的原始.NET 1.1版本中尚不存在它们.异步方法已添加在.NET 2.0 中，将这些元素添加到IDbCommand中将是一项重大更改(将成员添加到接口对于该接口的实现者来说是一项重大更改).
IDbCommand does not have the begin/end async methods because they did not yet exist in the original .NET 1.1 release of ADO.NET, and when the async methods were added in .NET 2.0 it would have been a breaking change to add those to IDbCommand (adding members to an interface is a breaking change for implementors of that interface).
我不知道为什么BeginExecuteScalar不存在，但是可以将其实现为环绕BeginExecuteReader的扩展方法.总之，在.NET 4.5中，我们现在有了ExecuteScalarAsync，它更易于使用.
I don't know why BeginExecuteScalar doesn't exist, but it can be implemented as an extension method that wraps around BeginExecuteReader. Anyway in .NET 4.5 we now have ExecuteScalarAsync which is easier to use.
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