Hello Is it possible to store the result of a stored procedure as a true/false value in a bool variable? Something like:
1)
bool var = ExecuteScalar("sp_name", parameters);
or
2)
bool var = ClassName.getValue(parameters);
where
getValue() is a method that has this code:
return dataBase.ExecuteDataSet("sp_name", parameters);
I want to know if a customer has a card or not. I was thinking of using what I have right now which is basically the second option above, and then create a condition whether the row count is more than zero. But I also want to know if there are any other methods I can use.
Thanks in advance.
You can simply do:
DataSet ds = dataBase.ExecuteDataSet("sp_name", parameters);
return ds.Tables[0].Rows.Count>0; //true if record found; false if no rows
Assuming your proc is simply doing a select using the parameters in the where clause. Something like:
select col1 from table a where condition=#parameter
You don't say which DBMS you are using. SQL Server, for example, does not have a bool data type, but you can make your sproc return an int, which you can test for nonzero, e.g.
bool result = ((int) ExecuteScalar("sp_name", parameters)) != 0;
NOTE: I have not tested this, but you could try making the sproc return a bit instead. This is still an integer value as far as SQL Server is concerned, but ADO.NET should detect it and automatically cast it to bool for you. It certainly does for sproc parameters.
ExecuteScalar returns an Object. So no, #1 above would throw an error. Assuming your stored procedure returns a value that can be converted to true/false, you'd have to do something like this:
bool var;
bool.TryParse(ExecuteScalar("sp_name", paramaters).ToString(), out var);
Related
I have the following part in the end of a SQL Server stored procedure:
if(#someValue < 0)
begin
SELECT #resultIsSuccess = 0
Return #resultIsSuccess
end
else
begin
SELECT #resultIsSuccess = 1
Return #resultIsSuccess
end
where #resultIsSuccess is of type bit.
So, basically I am returning a bool to indicate if the procedure yielded the intended result.
On the EF side, I configured the Function Import's return type as boolean.
When I call:
bool isSuccess = context.MyFunctionImport(arg1, arg2).FirstOrDefault().Value;
I get the following exception:
The data reader returned by the store data provider does not have
enough columns for the query requested.
What is the problem here?
If you are returning a value, you need a return parameter. Therefore you aren't using a datareader to get your value. You aren't selecting anything therefore you would need to have access to that return parameter.
Instead select your values to populate the datareader since you are probably getting an error when you try to read values from a noninstantiated datareader through EF.
if(#someValue < 0)
SELECT 0
else
SELECT 1
I'm unsure if return values are supported, reference, so you may be trying to do the impossible unless fixed in a newer version.
You have to keep in mind that you are NOT returning a bit datatype from your procedure. The return datatype of a stored procedure is int.
You could greatly simplify your code to a single line return statement.
return case when #someValue < 0 then 0 else 1 end
Then in your code you would need to parse the 0 or 1 to a boolean.
--EDIT--
Since you are looking for the first value you will need to use a select statement in your procedure. Something like this.
Select isSuccess = case when #someValue < 0 then 0 else 1 end
I'm trying to check if some user exists in my database or not using this stored procedure:
ALTER PROCEDURE see_if_writer_exsists_or_not
#username nvarchar(50),
#password nvarchar(50)
AS
select count(*)
from writers
where username = #username and password = #password
RETURN
Then I invoke it as a method using Linq-to-SQL with this code:
int b = DS.see_if_writer_exsists_or_not(username.Text, password.Text);
if (b > 0)
{ // the rest of the code...
but a conversion error appears
Cannot implicitly convert type'System.Data.Linq.ISingleResult' to 'int'
How to fix this ?
Note: I've tried Convert.ToInt32 method and it didn't work!
there is no problem with the stored procedure! if u want to check about if this username and password exists
just check if your method returns values or not by using .count()
if (DS.see_if_writer_exsists_or_not(username.Text, password.Text).count() > 0)
{
// yourcode...
}
I have found a solution for this also to extract my retrieved record from the database by using .ElementAt(0)method ,and here is the update in my code :
DS.see_if_writer_exsists_or_not(username.Text, password.Text).ElementAt(0)
by using this I could get the first element retrieved and that's what I wanted
It's just like the error message says:
Your call to see_if_writer_exsists_or_not returns an ISingleResult instance.
A call of ToString() returns "System.Data.Linq.ISingleResult" (which of course cannot be cast to an int).
You must return the query result from your stored proc and regenerate the see_if_writer_exsists_or_not method to accomplish what you want.
ISingleResult is an enumerable. You can loop through it using foreach. You can also do something like this:
ISingleResult<int> results = YourMethodCall();
int returnValue;
if(results.Count()>0){
returnValue = results.First<int>();
}
Also, please remove ToString call from your method call.
I'm trying to execute a store procedure like this:
public bool Test(){
var searchItem=base.Database.SqlQuery<QueryEntity>("exec nameOfMyProcedure #param1={0}",param13).FirstOrDefault();
if(searchItem!=null){
return searchItem.Output1;
}
else{
return false;
}
private class QueryEntity{
public bool Output1{get;set;}
}
I've one Return in the stored procedure
Unfortunately, searchItem always returns null.
Have you an idea how I can resolve that?
I'm using SQL server and C#.
Your stored procedure is returning more that one columns. That can be the reason for the error you are getting.
You can try something like this
base.Database.SqlQuery<IEnumerable<string>>("exec nameOfMyProcedure #param1={0},#param2={1},#param3={2}",param1,param2,param3)
basically this is an example and you need to do is, look into the structure of what your stored procedure returns and then use suitable object for parsing.
Here i am assuming all the returns values are string.
Find the solution.
It's not really proper but.. It's work
I create a new stored procedure which return 1 output like this
Select #Return_value as Return
instead of
Return #Return_value
My function isn't returning anything - strReturn is empty:
try
{
SqlParameter[] parameter = new SqlParameter[]
{
new SqlParameter("#MerchantID", MercahntID),
new SqlParameter("#LoactionID", LoactionID)
};
SqlHelper.ExecuteNonQuery(DbConnString, System.Data.CommandType.StoredProcedure, "GetMerchantLocationZip", parameter);
return strReturn;
}
catch (Exception ex)
{
LogError("Error Occurred When Retrieving Mercahnt Location Zip: MercahntID:" + MercahntID.ToString(), ex);
return strReturn;
}
}
When I execute this stored proc using 'exec GetMerchantLocationZip (3333, 373773)' I get the correct zipcode in SQL. Why don't I get it in Visual Studio?
Create PROCEDURE [dbo].[GetMerchantLocationZip](
#MerchantID bigint,
#LoactionID bigint)
AS
Begin
Select Zip FROM Merchant_Location
where MerchantID=#MerchantID AND LocationID =#LoactionID
End
I am learning, so apologies if it's a obvious error. Thanks all!
You're not getting results because you're not executing the code as a Query.
You're calling SqlHelper.ExecuteNonQuery() which doesn't return any results.
It looks like you're using the SqlHelper application block, so I think the code you want would be (if you're returning multiple rows in the query):
DataSet ds = SqlHelper.ExecuteDataSet(DbConnString,
CommandType.StoredProcedure,
"GetMerchantLocationZip",
parameter);
ds will then contain the results of the query.
If you're trying to retrieve a single value from the database rather than a set of rows, then your code would be:
object zip = SqlHelper.ExecuteScalar(DbConnString,
CommandType.StoredProcedure,
"GetMerchantLocationZip",
parameter);
You don't appear to be assigning anything to strReturn anywhere. You would also need to use ExecuteScalar to retrieve the value from a single row, single column result set.
strReturn = SqlHelper.ExecuteScalar(...) as string;
Or an OUTPUT parameter with ExecuteNonQuery.
You are calling ExecuteNonQuery which only returns the number of rows affected. Try this:
var zipCode = SqlHelper.ExecuteScalar(DbConnString, System.Data.CommandType.StoredProcedure, "GetMerchantLocationZip", parameter);
You are using ExecuteNonQuery which doesn't return results, it's just going to return the number of rows updated. You want to execute a reader.
You probably want to call the ExecuteScalar instead of ExecuteNonQuery as that is expected to have no return.
Perhaps the following code
var zipObject = SqlHelper.ExecuteScalar(DbConnString, System.Data.CommandType.StoredProcedure, "GetMerchantLocationZip", parameter);
return (string)zipObject;
strReturn isn't being set, and you need to call ExecuteScalar instead of ExecuteNonQuery.
Check your spelling!! You're probably throwing an exception in the SQL statement because you've misspelled "Merchant" or "Location" somewhere (or many places).
And, as others have pointed out, you probably want this:
return SqlHelper.ExecuteScalar(DbConnString,
System.Data.CommandType.StoredProcedure,
"GetMerchantLocationZip", parameter);
I have a table that has a field, "IsActive," that indicates whether a record has been "deleted" or not.
Currently, I retrieve this info like so:
public DataTable GetContractors(bool IsActive)
{
SqlParameter paramIsActive = new SqlParameter("#IsActive", SqlDbType.Bit);
paramIsActive.Value = IsActive;
DataSet ds = this.SQLDataAccess.ExecSProcReturnDataset(this.AppConfig.ConnectString, "p_selContractors", paramIsActive);
return ds.Tables[0];
}
The code for my DAL and stored procedure is irrelevant, so I'll omit that for now.
Here is my question: this code works fine if I want to return records that ARE active or ARE NOT active... but, how would I modify this to return ALL records (active AND inactive)?
Right now, I have two methods and two stored procs (one with the IsActive parameter and the other without the param), but I know there must be an easier way.
Any suggestions?
Pass a NULL (assign DBNull.Value to the parameter) and modify your stored procedure to check for that and not care what type of record it is in that circumstance. Some thing like:
.... WHERE MyTable.IsActive = COALESCE(#IsActive, MyTable.IsActive)
Make #IsActive nullable and tweak your SQL code like this:
select ... from ... t
where ...
and (#IsActive is null or t.IsActive = #IsActive)
Plus, refactor your code a tad so that it's more explicit:
public DataTable GetContractors(bool isActive)
{
return GetContractors((bool?)isActive);
}
public DataTable GetAllContractors()
{
return GetContractors(null);
}
private DataTable GetContractors(bool? isActive)
{
SqlParameter paramIsActive = new SqlParameter("#IsActive", SqlDbType.Bit);
paramIsActive.Value = isActive == null ? DBNull.Value : (object)isActive.Value;
DataSet ds = this.SQLDataAccess.ExecSProcReturnDataset(
this.AppConfig.ConnectString, "p_selContractors", paramIsActive);
return ds.Tables[0];
}
change your stored procedure. Have it check if the parameter is null. if it's null, return both active and not active. if it's not null, return the data depending on the parameter.
then in your code, make the parameter nullable, and pass a null when you want to return all records.
In your sproc, make the #isActive parameter nullable
ALTER PROCEDURE p_selContractors ( #isActive bit = null )
Then in your WHERE clause, use the following :-
WHERE
( #isActive IS NULL OR Active = #isActive )
And in your C# code, don't set the #isActive parameter value, and you should be cool.
A quick and easy hack would be to call both procedures seperately and merge the results.
(I'm not saying this is the best option, just one that no-one has suggested yet)
i.e.
var dt = this.SQLDataAccess.ExecSProcReturnDataset(this.AppConfig.ConnectString, "p_selContractors", true).Tables[0];
var dt2 = this.SQLDataAccess.ExecSProcReturnDataset(this.AppConfig.ConnectString, "p_selContractors", false).Tables[0];
dt.Merge(dt2, false);