Using _webDataDBContext As New WebDataEntities()
Dim results = _webDataDBContext.coverageareas.Select(Function(x) x)
If String.IsNullOrEmpty(city) = False Then
results.Where(Function(x) x.City = city)
End If
If String.IsNullOrEmpty(county) = False Then results.Where(Function(x) x.County = county)
If String.IsNullOrEmpty(state) = False Then results.Where(Function(x) x.State = state)
If String.IsNullOrEmpty(zip) = False Then results.Where(Function(x) x.Zip = zip)
Return Await results.ToArrayAsync()
End Using
Not sure why this isn't working, when my if statements are satisfied I want to append a where statement to my results.
However these where's are not being added even though the statements are satisfied. Anyone know why?
You have to assign the Where statement to the IQueryable.
results = results.Where(...)
Related
I have problem with Entity Core 3.1.2.
I have code like this:
SQL.Database.EnsureCreated();
var ThisCollector = SQL.CollectorServers
.Where(esa => esa.ServerName == ServerCollectorName)
.FirstOrDefault();
while (foo)
{
await SQL.Entry(ThisCollector)
.ReloadAsync();
DateTime dtTimeOut = DateTime.UtcNow.AddMinutes(-1);
//check status of current Worker
var CurrentLB = SQL.CollectorServers
.Where(esa => esa.isWorker == true
&& esa.LastSeenLB < dtTimeOut)
.FirstOrDefault();
if (CurrentLB!=null) //Current Worker is dead!
{
CurrentLB.isWorker = false;
ThisCollector.isWorker = true;
SQL.SaveChanges(); //This works allways
}
var Collectors = SQL.CollectorServers
.Where(Esa => Esa.isWorker == true);
if (Collectors.Count() == 0)
{
ThisCollector.isWorker = true;
SQL.SaveChanges();
}
if (Collectors.Count() >= 2)
{
foreach(CollectorServer cs in Collectors)
{
cs.isWorker = false;
//why this is requied?
SQL.Entry(cs).State = Microsoft.EntityFrameworkCore.EntityState.Modified;
}
ThisCollector.isWorker = true;
//<--This works only once, without manually setting State to
// modified!!! Why? Values has been changed from external program.
//(Management studio in this case)
SQL.SaveChanges();
}
await Task.Delay(10000, stoppingToken);
}
Problem is that last SaveChanges works only first time it has been called without I set Entry state to Modified. After that it does not make SQL query (I can see that in SQL Profiler).
In this case this can be fixed by this way, but I'm trying to undestand why this happends. My software saves lot data to SQL, and I need to know can I trust to this code without opening all queries and adding this modified state.
I didin't have this kind of problems in full version (6) of Entity, this is something quite new for me.
The described behavior would make sense if the entities returned by CollectorServers are not tracked.
ThisCollector is attached on every loop by the call to SQL.Entry(ThisCollector) :
await SQL.Entry(ThisCollector) //Attaching
.ReloadAsync(); //Reloading
Any changes made to it would be tracked and saved by the first call to DbContext.SaveChanges().
On the other hand, the entities returned by the Collectors query :
var Collectors = SQL.CollectorServers
.Where(Esa => Esa.isWorker == true);
Would remain untracked, until they get reattached by the call to SQL.Entry(cs) :
foreach(CollectorServer cs in Collectors)
{
cs.isWorker = false;
SQL.Entry(cs).State = Microsoft.EntityFrameworkCore.EntityState.Modified;
}
That's equivalent to calling DbContext.Update to attach and set the state to Modified. Update is easier to read though :
foreach(CollectorServer cs in Collectors)
{
cs.isWorker = false;
SQL.Update(cs);
}
I'm trying to achieve dynamic filtering on a table. My UI has filters that can be enabled or disabled on demand, and as you can imagine, my query should be able to know when to add filters to the query.
What I have so far is that I check if the filter object has a value, and if it does it adds a where clause to it. Example:
var q1 = DBContext.Table1
if (!string.IsNullOrEmpty(filterModel.SubjectContains))
q1 = q1.Where(i => i.Subject.Contains(filterModel.SubjectContains));
if (filterModel.EnvironmentId != null)
q1 = q1.Where(i => i.EnvironmentId == filterModel.EnvironmentId);
if (filterModel.CreatedBy != null)
q1 = q1.Where(i => i.CreatedByUserId == filterModel.CreatedBy);
var final = q1.Select(i => new
{
IssuesId = i.IssuesId,
Subject = i.Subject,
EnvironmentId = i.EnvironmentId,
CreatedBy = i.CreatedByUser.FullName,
});
return final.ToList();
The code above generates T-SQL that contains a WHERE clause for each field that uses AND to combine the conditions. This is fine, and will work for most cases.
Something like:
Select
IssueId, Subject, EnvironmentId, CreatedById
From
Table1
Where
(Subject like '%stackoverflow%')
and (EnvironmentId = 1)
and (CreatedById = 123)
But then I have a filter that explicitly needs an IssueId. I'm trying to figure out how the EF Where clause can generate an OR for me. I'm looking something that should generate a Tsql that looks like this:
Select
IssueId, Subject, EnvironmentId, CreatedById
From
Table1
Where
(Subject like '%stackoverflow%')
and (EnvironmentId = 1)
and (CreatedById = 123)
or (IssueId = 10001)
Found a solution for this that doesn't have to do multiple database call and works for me.
//filterModel.StaticIssueIds is of type List<Int32>
if (filterModel.StaticIssueIds != null)
{
//Get all ids declared in filterModel.StaticIssueIds
var qStaticIssues = DBContext.Table1.Where(i => filterModel.StaticIssueIds.Contains(i.IssuesId));
//Let's get all Issues that isn't declared in filterModel.StaticIssueIds from the original IQueryable
//we have to do this to ensure that there isn't any duplicate records.
q1 = q1.Where(i => !filterModel.StaticIssueIds.Contains(i.IssuesId));
//We then concatenate q1 and the qStaticIssues.
q1 = q1.Concat(qStaticIssues);
}
var final = q1.Select(i => new
{
IssuesId = i.IssuesId,
Subject = i.Subject,
EnvironmentId = i.EnvironmentId,
CreatedBy = i.CreatedByUser.FullName,
});
return final.ToList();
I am trying to look up record using if I have the key then use Find if not use Where
private ApplicationDbContext db = new ApplicationDbContext();
public bool DeactivatePrice(int priceId = 0, string sponsorUserName = "")
{
var prices = db.BeveragePrices;
// if we have an id then find
if (priceId != 0)
{
prices = prices.Find(priceId);
}
else
{
prices = prices.Where(b => b.UserCreated == sponsorUserName);
}
if (prices != null)
{
// do something
}
return true;
I get the following error for
prices = prices.Find(priceId);
Cannot convert app.Model.BeveragePrices from system.data.entity.dbset
I am copying the pattern from this answer but something must be different.
Seems you forgot to put a predicate inside the Find function call. Also you need to do ToList on the collection. The second option is a lot more efficient. The first one gets the whole collection before selection.
Another note commented by #Alla is that the find returns a single element. So I assume another declaration had been made for 'price' in the first option I state down here.
price = prices.ToList.Find(b => b.PriceId == priceId);
Or
prices = prices.Select(b => b.PriceId == priceId);
I assume the field name is PriceId.
In the following image you can see where i put the breakpoint and then debugged two step. You can also see that both assignments worked great they have the same count and are the same.
However if I do the following. Run the exact same call but only break on the third line directly then this happnes
set.QuestionSet.Questions should have count of 8 BEFORE the assigment, so it seems it's not properly assigned for some reason. I suspect this has something to do with how I fetch my data from DB.
Question and QuestionSet are normal POCOs and here is the code for the entire method.
public IEnumerable<QuestionSet> SearchAndFilterQuestionsAndSets(string searchString, int nrPerPage, int page, out int totalSearchCount)
{
searchString = searchString.ToLower();
List<QuestionSet> finalList = new List<QuestionSet>();
var result = ActiveContext.QuestionSets
.Select(x => new
{
QuestionSet = x,
Questions = x.Questions.Where(
y =>
y.Description.ToLower().Contains(searchString)
).OrderBy(
z => z.Description
)
})
.ToList();
foreach (var set in result)
{
//If our search matched the set itself we load all questions
if (set.QuestionSet.Name.ToLower().Contains(searchString))
{
//we dont bring empty sets
if (set.QuestionSet.Questions.Count() > 0)
{
set.QuestionSet.Questions = set.QuestionSet.Questions.ToList<Question>().OrderBy(x => x.Description).ToList<Question>();
finalList.Add(set.QuestionSet);
}
}
//We had one or more questions matching the search term
else if (set.Questions.Count() > 0)
{
var b = set.Questions.ToList<Question>();
set.QuestionSet.Questions = set.Questions.ToList<Question>();
finalList.Add(set.QuestionSet);
}
}
totalSearchCount = finalList.Count();
return finalList.Skip((page - 1) * nrPerPage).Take(nrPerPage);
}
UPDATE
If I do this instead in the failing else if
var a = new QuestionSet();
a.Id = set.QuestionSet.Id;
a.Name = set.QuestionSet.Name;
a.Questions = set.Questions.ToList<Question>();
finalList.Add(a);
Then it works, so the problem lies within the anonymous object, but why does it work when i step through with debugger and not otherwise?? call me puzzled.
Could be something to do with Late binding of anonymous types
I have a call made to Simple.Data where I want to limit the columns that are being brought back. However I am hitting problems..
This works fine:
var db = Database.Open();
var questionIdRow = db.Question.FindByFriendlyId(friendlyId);
if (questionIdRow == null) return Guid.Empty;
return questionIdRow.QuestionId;
However, the following doesn't work (I get a Simple.Data.UnresolvableObjectException 'Column not found')
var db = Database.Open();
var questionIdRow = db.Question.FindByFriendlyId(friendlyId)
.Select(db.Question.QuestionId);
if (questionIdRow == null) return Guid.Empty;
return questionIdRow.QuestionId;
I was under the impression from the Simple.Data documentation that this was all that I needed to do to limit the selected columns. Note that the selection is simply selecting the same column that is referenced later on.
The actual exception is thrown on the var questionIdRow = line.
Can anybody give me some guidance?
this is a common problem, and has actually led to FindBy being deprecated before we even get to 1.0. The problem is that FindBy returns a record straight away, so you can't continue to call query methods on it.
The correct approach is to call FindAllBy and end with a First or FirstOrDefault:
var db = Database.Open();
var questionIdRow = db.Question.FindAllByFriendlyId(friendlyId)
.Select(db.Question.QuestionId)
.FirstOrDefault();
if (questionIdRow == null) return Guid.Empty;
return questionIdRow.QuestionId;