使用async/await将现有的C#同步方法转换为异步方法? [英] Convert existing C# synchronous method to asynchronous with async/await?

问题描述

从同步I/O绑定方法(如下)开始，如何使用async/await使它异步?

Starting with a synchronous I/O bound method (below), how do I make it asynchronous using async/await?

public int Iobound(SqlConnection conn, SqlTransaction tran)
{
    // this stored procedure takes a few seconds to complete
    SqlCommand cmd = new SqlCommand("MyIoboundStoredProc", conn, tran);
    cmd.CommandType = CommandType.StoredProcedure;

    SqlParameter returnValue = cmd.Parameters.Add("ReturnValue", SqlDbType.Int);
    returnValue.Direction = ParameterDirection.ReturnValue;
    cmd.ExecuteNonQuery();

    return (int)returnValue.Value;
}

MSDN示例都假定存在* Async方法，并且没有为使自己从事I/O绑定操作提供任何指导.

MSDN examples all presume the preexistence of an *Async method and offer no guidance for making one yourself for I/O-bound operations.

我可以在新任务中使用Task.Run()并执行Iobound()，但是不鼓励创建新的Task，因为该操作不受CPU限制.

I could use Task.Run() and execute Iobound() within that new Task, but new Task creation is discouraged since the operation is not CPU-bound.

我想使用async/await，但是在这个基本问题上，我仍然停留在这里，该问题是如何进行此方法的转换的.

I'd like to use async/await but I'm stuck here on this fundamental problem of how to proceed with the conversion of this method.

推荐答案

此特定方法的转换非常简单:

Conversion of this particular method is pretty straight-forward:

// change return type to Task<int>
public async Task<int> Iobound(SqlConnection conn, SqlTransaction tran) 
{
    // this stored procedure takes a few seconds to complete
    using (SqlCommand cmd = new SqlCommand("MyIoboundStoredProc", conn, tran)) 
    {
        cmd.CommandType = CommandType.StoredProcedure;
        SqlParameter returnValue = cmd.Parameters.Add("ReturnValue", SqlDbType.Int);
        returnValue.Direction = ParameterDirection.ReturnValue;
        // use async IO method and await it
        await cmd.ExecuteNonQueryAsync();
        return (int) returnValue.Value;
    }
}

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