[英]Return one row from stored procedure in asp.net
I one to create a stored procedure to retrieve one row in the table: 我创建一个存储过程来检索表中的一行:
create procedure LogInUser
@username nvarchar(64),
@password nvarchar(64),
@succeed bit out,
@not_exist_err bit out
as
declare @exist_user nvarchar(64)
select @exist_user = username from users
where username = @username
if @exist_user is null
begin
set @succeed = 0
set @not_exist_err = 1
return
end
else
begin
select * from users
where username = @username and password = @password
end
return
First, I verify if a user exist or not by using: 首先,通过使用以下命令验证用户是否存在:
select @exist_user = username from users
where username = @username
Then get the row with every column: 然后获取每一列的行:
select * from users
where username = @username and password = @password
However, by using SqlDataReader
, the program won't enter the while loop to retrieve the information. 但是,通过使用SqlDataReader
,程序将不会进入while循环以检索信息。
It just don't enter the loop. 它只是不进入循环。 I don't understand why, even I executed it using SQL Server like this, it did return a row: 我不明白为什么,即使使用这样的SQL Server执行它,它也确实返回了一行:
declare @succeedResult bit
declare @existErr bit
exec LogInUser @username=admin, @password =admin, @succeed = @succeedResult, @not_exist_err = @existErr
EDIT : The C# method which executes the store procedure: 编辑 :执行存储过程的C#方法:
public User LogIn(User usr)
{
SqlConnection conn = A2.Controller.Utils.conn;
SqlCommand loginCmd = new SqlCommand("LogInUser", conn);
loginCmd.CommandType = CommandType.StoredProcedure;
User result = new User();
try
{
conn.Open();
loginCmd.Parameters.Add("@username", SqlDbType.NVarChar).Value = usr.Username;
loginCmd.Parameters.Add("@password", SqlDbType.NVarChar).Value = usr.Password;
loginCmd.Parameters.Add("@succeed", SqlDbType.Bit).Direction = ParameterDirection.Output;
loginCmd.Parameters.Add("@not_exist_err", SqlDbType.Bit).Direction = ParameterDirection.Output;
SqlDataReader dr = loginCmd.ExecuteReader();
if (loginCmd.Parameters["@succeed"].Value != DBNull.Value){
Console.WriteLine("User does not exist");
SqlParameter notExistErr = loginCmd.Parameters["@not_exist_err"];
if (notExistErr.Value != DBNull.Value){
throw new NotExistException("The username or password is incorrect.", "Users");
}
}
while (dr.Read()) {
Console.WriteLine("Looping dr");
result.Username = (string) dr["username"];
result.Password = (string) dr["password"];
result.FirstName = (string) dr["first_name"];
result.MiddleName = (string) dr["middle_name"];
result.LastName = (string) dr["last_name"];
result.ManagerID = (int) dr["manager_id"];
result.IsAdmin = (int) dr["is_admin"];
return result;
}
Console.WriteLine("Done reading");
}
finally {
if (conn.State == ConnectionState.Open) conn.Close();
}
return result;
}
Output parameters are only filled after you read the last row from the last result set in the procedure. 仅在您从过程中的最后一个结果集中读取了最后一行后,才填充输出参数。 So this part won't work: 因此,这部分将不起作用:
SqlDataReader dr = loginCmd.ExecuteReader();
if (loginCmd.Parameters["@succeed"].Value != DBNull.Value){
At this point loginCmd.Parameters["@succeed"].Value
is not set: it will be set only after you've read the last row, and dr.Read()
has returned false
. 此时,未设置loginCmd.Parameters["@succeed"].Value
:只有在您读完最后一行并且dr.Read()
返回false
之后,才会设置该值。
As a best practice, don't use output
parameters in stored procedures that return rowsets. 最佳做法是,不要在返回行集的存储过程中使用output
参数。
You can check whether your query returns the result or is not using dr.HasRows
, and it should look like... 您可以检查查询是否返回结果,或者不使用dr.HasRows
,它应该看起来像...
SqlDataReader dr = loginCmd.ExecuteReader();
if (!dr.HasRows)
{
Console.WriteLine("User does not exist");
SqlParameter notExistErr = loginCmd.Parameters["@not_exist_err"];
if (notExistErr.Value != DBNull.Value)
{
throw new NotExistException("The username or password is incorrect.", "Users");
}
}
else
{
while (dr.Read())
{
Console.WriteLine("Looping dr");
result.Username = (string) dr["@username"];
result.Password = (string) dr["@password"];
result.FirstName = (string) dr["@first_name"];
result.MiddleName = (string) dr["@middle_name"];
result.LastName = (string) dr["@last_name"];
result.ManagerID = (int) dr["@manager_id"];
result.IsAdmin = (int) dr["@is_admin"];
return result;
}
}
Something is strange -- I would expect your test to look like this: 有点奇怪-我希望您的测试看起来像这样:
declare @succeedResult bit
declare @existErr bit
exec LogInUser @username=N'admin', @password =N'admin', @succeed = @succeedResult, @not_exist_err = @existErr
But this brings up the simple answer.... are you calling your function with valid (ie exist) for username AND password? 但是,这引出了一个简单的答案。...您是否使用有效(即存在)的用户名和密码来调用函数?
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