If i have a table as called "users" and i want give only a query for example to show user as have id > 1.
How to do that in ASP.NET Core.
in php you can do like that:
$sql = "SELECT * FROM users WHERE id='1';";
but how to do same with ASP.NET CORE.
Sorry for my bad English.
You can use the FromSqlRaw extension method to begin a LINQ query based on a raw SQL query. FromSqlRaw can only be used on query roots, that is directly on the DbSet<>.
Note:DbSet.FromSql prior to Entity Framework Core 3.0
For parameterized queries , you could refer to the below examples:
1)Format string
var author = db.Authors.FromSqlRaw("SELECT * From Authors Where AuthorId = {0}", id).FirstOrDefault();
2)Create DbParameter objects for the provider that you are using.
var p1 = new SqliteParameter("#Id", id); // parameter construction for SqLite
var author = db.Authors.FromSqlRaw($"SELECT * From Authors Where AuthorId = #Id", p1).FirstOrDefault();
Reference:
https://learn.microsoft.com/en-us/ef/core/querying/raw-sql
https://www.learnentityframeworkcore.com/raw-sql
Related
in my [projest I'm using the MySQL Connector and Entity Framework. I have problem with the following code:
int now = DateTime.Now.DayOfYear;
var items = (from e in db.Table1
let date = e.Created.AddDays(90)
where date.DayOfYear > now
select e).ToList();
but I get the error message:
LINQ to Entities does not recognize the method 'System.DateTime AddDays(Double)'
method, and this method cannot be translated into a store expression.
how to fix it ?
You can not use these type of functions in linq queries you should Subtract 90 days from Now and then do the compare in your query
int now = DateTime.Now.DayOfYear.AddDays(-90);
var items = (from e in db.Table1
where e.Created > now
select e).ToList();
I'm using Linq to query MS CRM 2011 Web Services. I've got a query that results in very poor SQL, it fetches too much intermediary data and its performance is horrible!! I'm new to it, so it may very well be the way I'm using it...
I've got two entities linked via an N-N relationship: Product and SalesLink. I want to recover a bunch of Product from their SerialNumber along with all SalesLink associated to them.
This is the query I have using PredicateBuilder:
// Build inner OR predicate on Serial Number list
var innerPredicate = PredicateBuilder.False<Xrm.c_product>();
foreach (string sn in serialNumbers) {
string temp = sn; // This temp assignement is important!
innerPredicate = innerPredicate.Or(p => p.c_SerialNumber == temp);
}
// Combine predicate with outer AND predicate
var predicate = PredicateBuilder.True<Xrm.c_product>();
predicate = predicate.And(innerPredicate);
predicate = predicate.And(p => p.statecode == (int)CrmStateValueType.Active);
// Inner Join Query
var prodAndLinks = from p in orgContext.CreateQuery<Xrm.c_product>().AsExpandable()
.Where(predicate)
.AsEnumerable()
join link in orgContext.CreateQuery<Xrm.c_saleslink>()
on p.Id equals link.c_ProductSalesLinkId.Id
where link.statecode == (int)CrmStateValueType.Active
select new {
productId = p.Id
, productSerialNumber = p.c_SerialNumber
, accountId = link.c_Account.Id
, accountName = link.c_Account.Name
};
...
Using SQL profiler, I saw that it causes an intermediate SQL query that has no WHERE clause, looking like this:
select
top 5001 "c_saleslink0".statecode as "statecode"
...
, "c_saleslink0".ModifiedOnBehalfByName as "modifiedonbehalfbyname"
, "c_saleslink0".ModifiedOnBehalfByYomiName as "modifiedonbehalfbyyominame"
from
c_saleslink as "c_saleslink0" order by
"c_saleslink0".c_saleslinkId asc
This returns a huge amount of (useless) data. I think the join is done on the client side instead of on the DB side...
How should I improve this query? I runs in around 3 minutes and that's totally unacceptable.
Thanks.
"Solution"
Based on Daryl's answer to use QueryExpression instead of Linq to CRM, I got this which gets the exact same result.
var qe = new QueryExpression("c_product");
qe.ColumnSet = new ColumnSet("c_serialnumber");
var filter = qe.Criteria.AddFilter(LogicalOperator.Or);
filter.AddCondition("c_serialnumber", ConditionOperator.In, serialNumbers.ToArray());
var link = qe.AddLink("c_saleslink", "c_productid", "c_productsaleslinkid");
link.LinkCriteria.AddCondition("statecode", ConditionOperator.Equal, (int)CrmStateValueType.Active);
link.Columns.AddColumns("c_account");
var entities = serviceProxy.RetrieveMultiple(qe).Entities.ToList();;
var prodAndLinks = entities.Select(x => x.ToEntity<Xrm.c_product>()).Select(x =>
new {
productId = x.c_productId
, productSerialNumber = x.c_SerialNumber
, accountId = ((Microsoft.Xrm.Sdk.EntityReference)((Microsoft.Xrm.Sdk.AliasedValue)x["c_saleslink1.c_account"]).Value).Id
, accountName = ((Microsoft.Xrm.Sdk.EntityReference)((Microsoft.Xrm.Sdk.AliasedValue)x["c_saleslink1.c_account"]).Value).Name
}).ToList();
I really would have liked to find a solution using Linq, but it seems to Linq to CRM is just not there yet...
95% of the time when you're having performance issues with a complicated query in CRM, the easiest way to improve the performance is to run a straight SQL query against the database (assuming this is not CRM online of course). This may be one of the 5% of the time.
In your case, the major performance issue you're experiencing is due to the predicate builder forcing a CRM Server (not the SQL database) side join of data. If you used a Query Expression (which is what your link statement get's translated) you can specify a Condition Expression with an IN operator that would allow you to pass in your serialNumbers collection. You could also use FetchXml as well. Both of these methods would allow CRM to perform a SQL side join.
Edit:
This should get you 80% of the way with Query Expressions:
IOrganizationService service = GetService();
var qe = new QueryExpression("c_product");
var filter = qe.Criteria.AddFilter(LogicalOperator.Or);
filter.AddCondition("c_serialnumber", ConditionOperator.In, serialNumbers.ToArray());
var link = qe.AddLink("c_saleslink", "c_productid", "c_productsaleslinkid");
link.LinkCriteria.AddCondition("statecode", ConditionOperator.Equal, (int)CrmStateValueType.Active);
link.Columns.AddColumns("c_Account");
var entities = service.RetrieveMultiple(qe).Entities.ToList();
You will probably find you can get better control by not using Linq to Crm. You could try:
FetchXml, this is an xml syntax, similar in approach to tsql MSDN.
QueryExpression, MSDN.
You could issue a RetrieveRequest, blog.
I have a struts2 app with spring transactions and JPA2 over hibernate. The problem is that I have some rows in the database that are changed by an external source (some mysql triggers) and in my front app I have an ajax script that checks this values every 2 seconds. I always need to get the latest value, and not a cached one, and for this I found 2 solutions :
String sql = "FROM MyEntity WHERE xId=:id AND connect!=0 AND complete=0 AND (error=NULL OR error=0)";
Query q = this.em.createQuery(sql).setHint("org.hibernate.cacheable", false).setParameter("agId", agentId);
rs = q.getResultList();
if(rs.size() == 1){
intermedObj = (Intermed) rs.get(0);
}
and the other:
String sql = "FROM MyEntity WHERE xxId=:id AND connect!=0 AND complete=0 AND (error=NULL OR error=0)";
Query q = this.em.createQuery(sql).setParameter("agId", agentId);
rs = q.getResultList();
if(rs.size() == 1){
intermedObj = (Intermed) rs.get(0);
//get latest object from DB
em.refresh(intermedObj);
}
em is a instance of EntityManager which is managed by spring.
So, the question is: which is the best approach from these 2? Or maybe there is a better one ?
So you are right, I used hql there, I still have to learn a lot about hibernate an jpa, and java in general. So I guess that the correct way to write that cod in JPQL would be:
String sql = "SELECT m FROM MyEntity m WHERE m.xxId=:id AND m.connect!=0 AND m.complete=0 AND (m.error!=1)";
Query q = this.em.createQuery(sql).setParameter("agId", agentId);
rs = q.getResultList();
if(rs.size() == 1){
intermedObj = (Intermed) rs.get(0);
//get latest object from DB
em.refresh(intermedObj);
}
So the question would be, is this the proper way to make sure that I got the latest row from DB and not a cached record?
As regarding leve2 cache question I do not know if this is activated. How do I check that?
Is there a way to do a bulk update on a collection with LINQ? Currently if I have a List<myObject> and I want to update column1 to equal TEST for every row in the List I would setup a foreach loop and then for each individual object I would set the value and then save it. This works fine but I was just wondering if there was some LINQ method out there where I could do something like myOject.BulkUpdate(columnName, value)?
Your requirement here is entirely possible using Linq expressions and Terry Aney's excellent library on this topic.
Batch Updates and Deletes with LINQ to SQL
An update in the terms of the example you gave would be as follows:
using BTR.Core.Linq;
...
Context.myObjects.UpdateBatch
(
Context.myObjects.Where(x => x.columnName != value),
x => new myObject { columnName = value}
);
Edit (2017-01-20): It's worth nothing this is now available in the form of a NuGet package # https://www.nuget.org/packages/LinqPost/.
Install-Package LinqPost
Sounds like you're using LINQ To SQL, and you've got the basics laid out already.
LINQ To SQL is about abstracting tables into classes, and doesn't really provide the 'silver bullet' or one-liner you are looking for.
The only way to do that is to achieve your one-liner would be to make a stored proc to take that column name and new value, and implement that logic yourself.
db.MassUpdateTableColumn("Customer", "Name", "TEST");
....
CREATE PROC MassUpdateTableColumn
#TableName varchar(100), #ColumnName varchar(100), #NewVal varchar(100)
AS
/*your dynamic SQL to update a table column with a new val. */
Otherwise, it's as you describe:
List<Customer> myCusts = db.Customers.ToList();
foreach(Customer c in myCusts)
{
c.Name = "TEST";
}
db.SubmitChanges();
LINQ to SQL (or EF for that matter), is all about bringing objects into memory, manipulating them, and then updating them with separate database requests for each row.
In cases where you don't need to hydrate the entire object on the client, it is much better to use server side operations (stored procs, TSQL) instead of LINQ. You can use the LINQ providers to issue TSQL against the database. For example, with LINQ to SQL you can use context.ExecuteCommand("Update table set field=value where condition"), just watch out for SQL Injection.
EF Core 7.0 introduces Bulk Update and Bulk Delete.
For example, consider the following LINQ query terminated with a call to ExecuteUpdateAsync:
var priorToDateTime = new DateTime(priorToYear, 1, 1);
await context.Tags
.Where(t => t.Posts.All(e => e.PublishedOn < priorToDateTime))
.ExecuteUpdateAsync(s => s.SetProperty(t => t.Text, t => t.Text + " (old)"));
This generates SQL to immediately update the “Text” column of all tags for posts published before the given year:
UPDATE [t]
SET [t].[Text] = [t].[Text] + N' (old)'
FROM [Tags] AS [t]
WHERE NOT EXISTS (
SELECT 1
FROM [PostTag] AS [p]
INNER JOIN [Posts] AS [p0] ON [p].[PostsId] = [p0].[Id]
WHERE [t].[Id] = [p].[TagsId] AND [p0].[PublishedOn] < #__priorToDateTime_1)
I am implementing the asp.net MVC web application, where i am using the Linq to Sql to manipulate the data in database. but in my one of action, i want to insert multiple table entries which are depends upon each other by referring previous insertion Id's. So i just wnat to know how to handle the transaction, like begin transaction, commit,rollback and all like in ADO.net. how to manage this. what if one of insertion get crashed in the middle of manipulation?
Note:- I am not using the Stored procedures here. I am using Lambda expressions and methods. Also these are use in different manager classes.
Example:
For Create Subject - used method in SubjectManager class to insert subject infor, that returns subject Id. within this subjectid i am inserting the let say its chapters with another method in manager class as ChapterManager. which again returns the ChapterId, on base of this chapeter Id , inserting the Topics of chapter. that again uses Topic manager same like above.in each manger class i am creating dataContext object for the same. and I am controlling all this within a single action in my controller. but worrying about the transaction management. how I can use here ?
The DataContext already includes an embedded transaction object. For example, let's say you are placing a new order for a customer. You can set up your model so that the following code updates both the Customer AND Order table with a single SubmitChanges. As long as a foreign key relationship exists between the two tables, the embedded transaction object handles both the Customer update and the Order insert in the same transaction. Using a TransactionScope object to encase a single DataContext is redundant:
using (DataContext dc = new DataContext())
{
Order order = new Order();
order.ProductID = 283564;
order.Quantity = 7;
order.OrderDate = DateTime.Now;
Customer customer = dc.Customers.Single(c => c.CustomerID == 6);
customer.LastUpdate = order.OrderDate;
customer.Orders.Add(order);
dc.SubmitChanges();
}
using(TransactionScope scope = new TransactionScope())
{
using(DataContext ctx = new MyDataContext())
{
ctx.Subject.Add(subject);
Chapter chapter = new Chapter();
chapter.SubjectId = subject.Id;
ctx.SubmitChanges();
ctx.Chapter.Add(chapter);
ctx.SubmitChanges();
scope.Complete() // if it all worked out
}
}
From the System.Transactions namespace I believe.