I have a rather strange problem which is scratching my head at the moment. I am using EF together with MySQL for a project and when I want to update a record on the database like this
using (var context = new MyDbContext())
{
var record = (from d in context.Dictionary where d.CompanyName == companyName && d.Name == "Logo" select d).FirstOrDefault();
record.Value = _path;
context.SaveChanges();
}
Then every record that has d.Name == "Logo" gets updated for some reason, which means that it ignores the d.CompanyName == companyName part. Anyone who has experienced the same problem or know how to solve it?
Thanks in advance.
Actually I don't use EF Provider for MySQL often but I suppose it works.
The problem can be splitted in 2 parts, a select and an update. The select is fine, if you need to see what is the query you can split the select statement like this
var query = (from d in context.Dictionary where d.CompanyName == companyName && d.Name == "Logo" select d);
var record = query.FirstOrDefault();
and have a look to query variable (just point it in debug mode).
About your issue the only reason that I can immagine is that you did not configure the Dictionary class in the right way.
I mean, when you run context.SaveChanges an Update query is generated using the Key definition of Dictionary (the Where part of the query). If the key definition is wrong, the where clause will be wrong.
Use this I hope this will help you.
using (var context = new MyDbContext())
{
var record = context.Dictionary.Where(x=> x.CompanyName == companyName && x.Name == "Logo").FirstOrDefault();
record.Value = _path;
context.SaveChanges();
}
Related
I working with Database first C# MVC, EF6, LINQ and JSon to try and pass data to both Highcharts and Google Maps for some of my reporting.
If I could add an image I would show you the relevant portion of my model, but sadly I need more reputation to do that...
The portion of the Entity Model I'm concentrating on right now is based on a central Docket that contains a BuildingCode as part of a one-to-many relationship to a building with and address and further relationship to the buildings polygons (for mapping). Dockets are also classified by one or more DocketTypes and thus there is a many-to-many relationship between Dockets and DocketTypes, which is not directly exposed to through the EF.
As an example a Docket which represents an investigation, could be related to the theft of a mobile phone in building A located on Campus X, not only was the cellphone stolen but the assailant also assaulted the victim in order to steal the mobile phone. So there are 2 DocketTypes here 1. Theft of mobile phone and 2. assault. Note: this is fictitious and for illustration purposes only .
One of my fundamental reports requires that I count how many docketTypes affect each building and each campus in a given period. When I display this I also need to show what the DocketTypes are.
I have no end of nightmare trying to find a way to get this right, I keep running into circular reference errors and needing to use explicit conversions when trying to model the data with LINQ so that I can pass a single nested object through JSON to the client side where displaying will occur.
In the below code I am told I need an Explicit conversion:
Cannot implicitly convert type 'Campus_Investigator.ViewModels.DocketTypeViewModel' to 'System.Collections.Generic.IEnumerable<Campus_Investigator.ViewModels.DocketTypeViewModel>'. An explicit conversion exists (are you missing a cast?)
var currentDocketQuery = from d in db.Dockets
from dt in d.DocketTypes
from bp in d.BuildingDetail.BuildingPolygons
where d.OccurrenceStartDate >= datetime && d.BuildingDetail.CampusName == Campus
select new CampusBuildingDocketTypeViewModel()
{
BuildingCode = d.BuildingDetail.BuildingCode,
BuildingName = d.BuildingDetail.BuildingName,
//BuildingPolygons = d.BuildingDetail.BuildingPolygons,
DocketTypes = new DocketTypeViewModel()
{
Category = dt.Category,
SubCategory = dt.SubCategory,
ShortDescription = dt.ShortDescription
}
};
I appreciate any ideas on how I can explicitly convert this or is that a better method I can use and avoid the circular reference error?
You included some redundant part in your query (which performs some inner join). The from bp in d.BuildingDetail.BuildingPolygons is joined in but then is not shown in the result. So it totally does not make sense. There may be duplicated elements in the result due to that. The from dt in d.DocketTypes is wrong joined in, although you need it in the result but because the DocketTypes is output per d in db.Dockets, so it's just simply queried like this:
var currentDocketQuery = from d in db.Dockets
where d.OccurrenceStartDate >= datetime && d.BuildingDetail.CampusName == Campus
select new CampusBuildingDocketTypeViewModel()
{
BuildingCode = d.BuildingDetail.BuildingCode,
BuildingName = d.BuildingDetail.BuildingName,
//BuildingPolygons = d.BuildingDetail.BuildingPolygons,
DocketTypes = d.DocketTypes
};
In fact I can see the commented line //BuildingPolygons = d.BuildingDetail.BuildingPolygons, so if you want to include that, it should also work.
If the DocketTypes has different type of d.DocketTypes, then you need a simple projection like this:
var currentDocketQuery = from d in db.Dockets
where d.OccurrenceStartDate >= datetime && d.BuildingDetail.CampusName == Campus
select new CampusBuildingDocketTypeViewModel()
{
BuildingCode = d.BuildingDetail.BuildingCode,
BuildingName = d.BuildingDetail.BuildingName,
//BuildingPolygons = d.BuildingDetail.BuildingPolygons,
DocketTypes = d.DocketTypes.Select(e => new DocketTypeViewModel()
{
Category = e.Category,
SubCategory = e.SubCategory,
ShortDescription = e.ShortDescription
})
};
I managed to solve this one by using the below. The major hassle with this is the circular referencing that exists in the model. When JSON serializes these, everything falls apart so it takes a lot of transforming to make sure that I only extract what I need. In this case grouped campus and building data (below includes the polygons which where only half commented out in the above) and then the include the detail of the DocketTypes that occurred at each building.
var datetime = DateTime.Now.AddDays(-30);
var campusDocket = from d in db.Dockets
where d.OccurrenceStartDate >= datetime && d.BuildingDetail.CampusName == Campus
group d by new { d.BuildingDetail.CampusName, d.BuildingDetail.BuildingCode, d.BuildingDetail.BuildingName } into groupdata
select new CampusBuildingDocketTypeViewModel
{
BuildingCode = groupdata.Key.BuildingCode,
BuildingName = groupdata.Key.BuildingName,
CampusName = groupdata.Key.CampusName,
Count = groupdata.Count(),
BuildingPolygons = from bp in db.BuildingPolygons
where bp.BuildingCode == groupdata.Key.BuildingCode
select new BuildingPolygonViewModel
{
Accuracy = bp.Accuracy,
BuildingCode = bp.BuildingCode,
PolygonOrder = bp.PolygonOrder,
Latitude = bp.Latitude,
Longitude = bp.Longitude
},
DocketTypes = from doc in db.Dockets
from dt in doc.DocketTypes
where doc.OccurrenceStartDate >= datetime && doc.BuildingCode == groupdata.Key.BuildingCode
select new DocketTypeViewModel
{
Category = dt.Category,
SubCategory = dt.SubCategory,
ShortDescription = dt.ShortDescription
}
};
The Answer again is ViewModels. I'm finding ViewModels seem to solve a lot of problems...
I am using the following code to select every course from my a table with a bunch of courses - how would I change the code to narrow down the selection from every course to every course with the field db.Courses.myField = true?
var courses = from s in db.Courses
select s;
It's pretty simple ...
var courses = from s in db.Courses
where s.myField == true
select s;
Take a look at the data tutorials on asp.net.
Using Linq,
var courses = db.Courses.Where(s=>s.myField == true);
I'm developing a small filtering based on the 3 fields. I'm also using the MySQL Connector in my MVC 3 project.
I've found a nice looking PredicateBuilder http://www.albahari.com/nutshell/predicatebuilder.aspx . but it seems not to be working with the MySQL
var predicate = PredicateBuilder.False<Order>();
if(OrderID == 0)
predicate = predicate.And(x => x.OrderID == 9); //an example, that order exist in the DB
var result = (from x in db.Order select x).AsExpandable()
.Where(predicate).ToList();
but the result contains 0 elements. Why ?
Because you started with false and are using AND you will always get false. Start with True instead:
var predicate = PredicateBuilder.True<Order>();
I m just starting with microsoft (MVC,C#, LINQ), so far so good, but i have a question about LINQ uses, How do i get the value form a LINQ like this one?
var x = from a in db.tablex
where a.eventID == eventID
select new
{
owner = a.owner,
shipper = a.shipper,
consignee = a.consignee
};
I try something like "r.owner" inside a foreach to get the value retrieved from DB
foreach (var r in x)
but its not working.. i dont get intellisense either.. how do i get the value??. I saw several examples and it seems to work like this, but for some reason its not working.. Thanks
Ok guys here was the thing, (it wasnt the typo it was just in the post), i was missing a using :
using System.Reflection;
with this C# automatically creates a class from them, and now it works
What a noob of me =).
foreach (var r in x)
{
var owner = r.owner;// not x.owner
}
My appologies upfront for the lengthy question. I made quite an effort to make my question as clear as possible in one go. Please bear with me. ;o) any help will be greatly appreciated!
I have the classes Branch and Text:
class Branch
int ID
Text WebDescription
and a bunch of other properties
class Text
int ID
string UK
string NL
string FR
string IT
and a bunch of other properties as well
I want to only display the ID of the branch and its description in the appropriate language. I want only one query (no extra round trips) which retrieves only two fields (not the whole object).
I found three solutions
Via the object model in the query
// good: no round trips
// good: clean sql
// bad: impossible to use the currentUserLanguage parameter
var lang = "NL";
var dbProject = new ProjectDataContext();
var query = from b in dbProject.GetTable<Branch>()
select new
{
b.ID,
WebDescription = b.WebDescriptionObject.NL // <-- problem
};
var text = query.First().WebDescription;
Via the object model after the query
// good: no round trips (eager loading of text object)
// good: possible to use the currentUserLanguage parameter
// bad: loads the *whole* branch and text object, not just two fields
var lang= "NL";
var dbProject = new ProjectDataContext();
var query = from b in dbProject.GetTable<Branch>()
select new
{
b.ID,
WebDescription = b.GetWebDescriptionAsString(lang)
};
var text = query.First().WebDescription;
Using an expression
// good: I have the feeling I am on the right track
// bad: This doesn't work :o( throws an exception
var lang= "NL";
var dbProject = new ProjectDataContext();
var query = from b in dbProject.GetTable<Branch>()
select new
{
b.ID,
WebDescription = b.GetWebDescriptionAsExpression(lang)
};
var text = query.First().WebDescription;
Here is code for the two methods GetWebDescriptionAsString and GetWebDescriptionAsExpression.
public string GetWebDescriptionAsString(string lang)
{
if (lang== "NL") return WebDescriptionObject.NL;
if (lang== "FR") return WebDescriptionObject.FR;
if (lang== "IT") return WebDescriptionObject.IT;
return WebDescriptionObject.UK;
}
public Expression<Func<Branch, string>> GetWebDescriptionAsExpression(string lang)
{
if (lang== "NL") return b => b.WebDescriptionObject.NL;
if (lang== "FR") return b => b.WebDescriptionObject.FR;
if (lang== "IT") return b => b.WebDescriptionObject.IT;
return b => b.WebDescriptionObject.UK;
}
Without really answering the question, the cleanest approach would be to change the Text structure into a more normalized form like:
Text
ID
TextTranslation
ID
TextID
Lang
TextValue
where each text has a number of translations, one for each language.
The query would become something like:
var q =
from branch in dbProject.Branches
join text in dbProject.Texts on branch.TextID = text.ID
join translation in dbProject.TextTranslations on text.ID = translation.TextID
where translation.Lang == lang
select new
{
branch.ID,
WebDescription = translation.TextValue
};
This approach has other advantages as well, for example adding a new language will not change the model structure.
This would be very easy to do if you used a stored procedure. Are you opposed to using SP's as a solution?
If a stored procedure works, then I am happy to use it.
Thank you for you prompt reply.
I made a quick attempt. The UDF was already there, I just didn't know how to use it. The performance dropped significantly. The first solution is 3 times faster. In my understanding, this approach would require extra round trips to the database. Is that correct?
var query = from b in dbProject.GetTable<Branch>()
select new
{
b.ID,
WebDescription = db.fGetText(b.WebDescriptionID, (currentUserLanguage))
};
Without understanding your whole problem
create a stored procedure like this:
CREATE PROCEDURE spGetTheTextINeed #Language char(2), #BranchID int
AS
/* I don't know how your database is structured so you need to write this */
SELECT MyText from MyTable WHERE Language=#Language and Branch=#BranchID
Then you need to add the sp to your DBML and then you can just call the sp you need with the appropriate parameters:
var query = myDataContext.spGetTheTextINeed("NL",[your branch number])
Dim str As String
str = query.MyText
The code above is not to be exact - I don't understand your full requirements but this should get you started.