使用async/await将现有C#同步方法转换为异步？

Question

从同步I/O绑定方法开始(如下所示),如何使用async/await使其异步？

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示例都假设存在*Async方法,并且没有为I/O绑定操作自己创建一个指导.

我可以使用Task.Run()并在该新任务中执行Iobound(),但不鼓励创建新任务,因为该操作不受CPU限制.

我想使用async/await,但我仍然坚持这个如何继续转换此方法的基本问题.

Answer 1

转换此特定方法非常简单:

// 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;
    }
}