[英]Why does Dapper QueryAsync<T> behave differently from Query<T> with sproc return values?
我有一个存储过程执行检查,并返回行或非零返回值:
CREATE PROCEDURE dbo.ConditionalGet
@ID INT
AS
BEGIN
-- this is a silly made up condition just to test the issue
IF @ID % 2 = 1
BEGIN
RETURN -1
END
SELECT *
FROM MyTable
WHERE ID = @ID
RETURN 0
END
我有一个使用Dapper返回结果或引发异常的C#回购类:
public class Repo
{
public MyClass Get(int id)
{
using (var conn = GetSqlConnection())
{
var p = new { ID = id };
var pWithReturnValue = new DynamicParameters(p);
p.Add("return", null, DbType.Int32, ParameterDirection.ReturnValue);
var result = conn.Query<MyClass>("dbo.ConditionalGet", p, commandType: CommandType.StoredProcedure);
var errorCode = p.Get<int>("return");
if (errorCode != 0)
throw new RepositoryGetException(errorCode);
return result.FirstOrDefault();
}
}
}
这可以按预期工作:当id被2整除时,将返回水合对象,否则将引发异常。
但是,当我使代码异步时,这将失败!
public class Repo
{
public async Task<MyClass> Get(int id)
{
using (var conn = GetSqlConnection())
{
var p = new { ID = id };
var pWithReturnValue = new DynamicParameters(p);
p.Add("return", null, DbType.Int32, ParameterDirection.ReturnValue);
// this is the only change!
var result = await conn.QueryAsync<MyClass>("dbo.ConditionalGet", p, commandType: CommandType.StoredProcedure);
var errorCode = p.Get<int>("return");
if (errorCode != 0)
throw new RepositoryGetException(errorCode);
return result.FirstOrDefault();
}
}
}
这将引发InvalidOperationException“未选择任何列”!
我真的很喜欢这里的模式,并且想异步使用它,那为什么会失败呢? 我尝试过打开和关闭缓冲,但没有任何效果。
目前,Dapper不支持不执行SELECT语句的Async方法。
在Github中有一个开放的问题:
https://github.com/StackExchange/Dapper/issues/591
您现在要做的是:
ALTER PROCEDURE dbo.ConditionalGet
@ID INT,
@Output INT OUTPUT
AS
BEGIN
-- this is a silly made up condition just to test the issue
IF @ID % 2 = 1
BEGIN
SET @Output = -1
END
ELSE BEGIN
SET @Output = 0
END
SELECT *
FROM MyTable
WHERE ID = @ID
END
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