I trying write a generic method for create response to datatables ajax request;
public static Response<T> CreateResponse<T>(IQueryable<T> query, Request request) where T : class
{
query = query.AsNoTracking();
var filtered = query;
if (!string.IsNullOrEmpty(request.Search.Value))
{
var keywords = Regex.Split(request.Search.Value, #"\s+").ToList();
request
.Columns
.Where(p => p.Searchable)
.ToList()
.ForEach(c =>
keywords.ForEach(k =>
{
filtered = filtered.Intersect(query.Where(p => EF.Functions.Like(EF.Property<string>(p, c.Name), $"%{k}%")));
})
);
}
var ordered = filtered;
request.Order.ForEach(p => ordered = p.Dir == "asc" ? ordered.OrderBy(q => EF.Property<T>(q, request.Columns[p.Column].Name)) : ordered.OrderByDescending(q => EF.Property<T>(q, request.Columns[p.Column].Name)));
var paged = ordered.Skip(request.Start).Take(request.Length);
return new Response<T> { draw = request.Draw, recordsTotal = query.Count(), recordsFiltered = filtered.Count(), data = paged.ToList() };
}
My problem is, when query parameter is IIncludableQueryable EF.Property method can't locate sub properties. For example;
DataTables.CreateResponse<Rayon>(context.Rayons.Include(p=>p.User), parameters);
EF.Property<T>.Property<string>(p, "Name") is working but, EF.Property<T>.Property<string>(p, "User.Name") is not working, exception message is "EF.Property called with wrong property name."
Sorry for bad English.
Related
Please note this error message :
System.NotSupportedException: 'Could not parse expression
'value(Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable
This overload of the method 'System.Linq.Queryable.Except' is
currently not supported.'
Is supported in newer versions of ef core?
my code :
var tuple = SearchBrand(searchTerm);
var result = GetExceptionsBrand(tuple.Item1, categoryId);
return Json(new
{
iTotalDisplayRecords = tuple.Item2,
iDisplayedBrand = result
.Skip(page * 10)
.Take(10)
.ToList(),
});
public async Task<Tuple<IQueryable<BrandDto>, int, int>>SearchBrand(string searchTerm)
{
var result = _context.Brands
.Where(c => c.IsDeleted == displayIsDeleted)
.WhereDynamic(searchTerm)
return new Tuple<IQueryable<BrandDto>, int, int>(result,
filteredResultsCount, totalResultsCount);
}
public IQueryable<BrandDto> GetExceptionsBrand(IEnumerable<BrandDto> filteredBrand, int categoryId)
{
var query = _context.CategoriesBrands.Where(x => x.CategoryId == categoryId);
var selectedList = new List<BrandDto>();
foreach (var item in query)
{
var cb = new BrandDto()
{
BrandDto_BrandId = item.BrandId
};
selectedList.Add(cb);
}
IQueryable<BrandDto> ExcpetList = filteredBrand.AsQueryable().Except(selectedList, new ComparerBrand());
return ExcpetList;
}
I am using within my code some EF LINQ expressions to keep complex queries over my model in one place:
public static IQueryable<User> ToCheck(this IQueryable<User> queryable, int age, bool valueToCheck = true)
{
return queryable.Where(ToBeReviewed(age, valueToCheck));
}
public static Expression<Func<User, bool>> ToCheck(int age, bool valueToCheck = true)
{
return au => au.Status == UserStatus.Inactive
|| au.Status == UserStatus.Active &&
au.Age.HasValue && au.Age.Value > age;
}
I am then able to use them in queries:
var globalQuery = db.Users.ToCheck(value);
And also in selects:
var func = EntityExtensions.ToCheck(value);
var q = db.Department.Select(d => new
{
OrdersTotal = d.Orders.Sum(o => o.Price),
ToCheck = d.Users.AsQueryable().Count(func),
})
What I am trying to achieve is to actually use the same expression/function within a select, to evaluate it for each row.
var usersQuery = query.Select(au => new {
Id = au.Id,
Email = au.Email,
Status = au.Status.ToString(),
ToBeChecked = ???, // USE FUNCTION HERE
CreationTime = au.CreationTime,
LastLoginTime = au.LastLoginTime,
});
I am pretty that threre would be a way using plain EF capabilities or LINQKit, but can't find it.
Answering my own question :)
As pointed by #ivan-stoev, the use of Linqkit was the solution:
var globalQueryfilter = db.Users.AsExpandable.Where(au => au.Department == "hq");
var func = EntityExtensions.ToCheck(value);
var usersQuery = globalQueryfilter.Select(au => new
{
Id = au.Id,
Email = au.Email,
Status = au.Status.ToString(),
ToBeChecked = func.Invoke(au),
CreationTime = au.CreationTime,
LastLoginTime = au.LastLoginTime,
});
return appUsersQuery;
It's required to use the AsExpandable extension method from Linqkit along with Invoke with the function in the select method.
I want to add one more example:
Expression<Func<AddressObject, string, string>> selectExpr = (n, a) => n == null ? "[no address]" : n.OFFNAME + a;
var result = context.AddressObjects.AsExpandable().Select(addressObject => selectExpr.Invoke(addressObject, "1"));
Also, expression can be static in a helper.
p.s. please not forget to add "using LinqKit;" and use "AsExpandable".
Below find a method that does not work. We fail on the line query.Select(...
Below that find a method with hard coded object property names which does work. But, this method is obviously not dynamic, nor flexible. There may be many properties of a Customer I may wish to search on.
The error string is at bottom. I get it that somehow the LINQ to Entity is unable to deal with conversion of GetValue to some sort of TSQL. Would anyone know of how I might code this up?
public List<Customer> GetForQuery(params Tuple<string, string>[] keyValuePairs) {
using (var db = new DBEntities()) {
var availableProperties = typeof(Customer).GetTypeInfo().DeclaredProperties.ToList();
var query = db.Customers.Select(c => c);
foreach (Tuple<string, string> pair in keyValuePairs) {
PropertyInfo pi = availableProperties.First(p => p.Name.Equals(pair.Item1));
if (pi == null)
continue;
query = query.Where(u => pi.GetValue(u, null).ToString().StartsWith(pair.Item2));
}
var results = query.Select(c => c).ToList();
return results;
}
}
How I might call the above:
CustomerController custController = new CustomerController();
List<Customer> results = custController.GetForQuery(Tuple.Create<string, string>("FName", "Bob" ));
The working fixed method:
public List<Customer> GetForQuery(string firstName = "", string lastName = "", string phoneNumber = "") {
using (var db = new DBEntities()) {
var query = db.Customers.Select(c => c);
if (firstName.HasContent())
query = query.Where(u => u.FName.StartsWith(firstName));
if (lastName.HasContent())
query = query.Where(u => u.LName.StartsWith(lastName));
if (phoneNumber.HasContent())
query = query.Where(u => u.EveningPhone.StartsWith(phoneNumber));
var results = query.Select(c => c).ToList();
return results;
}
}
ERROR:
LINQ to Entities does not recognize the method 'System.Object GetValue(System.Object, System.Object[])' method, and this method cannot be translated into a store expression.
The Plan:
So now what I basically want is to take my propertys out of the class, let the user pick some and then pull a List with ONLY those propertys out of MongoDB.
The Code:
here is where the method starts:
private void DoStuffExecute(object obj)
{
Class class= new Class();
ExtractClass(class);
if (propList != null)
{
var result = classService.DoStuff(propList);
}
}
in "ExtractClass()" the Propertys are being pulled out of the Class.
void ExtractClass(object obj)
{
foreach (var item in obj.GetType().GetProperties())
{
propList.Add(item.Name);
}
}
and finally in "classService.DoStuff()" i try to set the "fields".
public List<class> DoStuff(List<string> Props)
{
try
{
var filter = Builders<class>.Filter.Empty;
var fields = Builders<class>.Projection.Include(x => x.ID);
foreach (var item in Props)
{
string str = "x.";
str += item.ToString();
fields = Builders<class>.Projection.Include(x => str);
fields = Builders<class>.Projection.Include(x => item);
}
var result = MongoConnectionHandler.MongoCollection.Find(filter).Project<class>(fields).ToList();
return result;
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
var result = new List<class>();
return result;
}
}
when i run the programm it gives me an "Unable to determine the serialization information for x=> value"... since im giving it a string.
The Question:
Does anyone have an Idea how to repair the code above or even make the plan work in another way?
thank you.
First of all: you are using such code lines as : var filter = Builders<class>.Filter.Empty; It is not possible, because class is a reserved keyword in c# (https://msdn.microsoft.com/en-us/library/x53a06bb.aspx) I assume, it's your Model, and i will speak about it as about Model class.
Include Filter needs Expression as a parameter, not a string, you should construct is as a expression. That's the second thing. Third, you should combine your includes as a chain, So your part of creating Include Filter from string List should look like:
var filter = Builders<Model>.Filter.Empty;
var fields = Builders<Model>.Projection.Include(x => x.Id);
foreach (var item in Props)
{
var par = Expression.Parameter(typeof(Model));
var prop = Expression.Property(par, item);
var cast = Expression.Convert(prop, typeof(object));
var lambda = Expression.Lambda(cast, par);
fields = fields.Include((Expression<Func<Model, object>>)lambda);
}
I have all expresiions separate for better understanding: first you create Parameter (x=>), than you add property (x=>x.Property1), than you should cast it to object, and after all create Lambda Expression from it.
And now the last part: You don't need all of it, Include function could get jsut a string as a parameter. So you could instead of all expression call write this:
fields = fields.Include(item);
Task: use different where clause in one query
Here is example (it is not real query, just to illustrate the problem)
var events = ctx.Events; // ctx - EntityFramework context
var res = events
.GroupBy(ee => ee.State)
.Select(gg => new
{
State = gg.Key,
FirstTwo = events
// how to get this clause from variable
.Where(ee => ee.State == gg.Key)
.Take(2)
})
.ToList();
Next code did not work, the problem is that where expression use parameter from query gg.Key
var events = ctx.Events;
var res = events
.GroupBy(ee => ee.State)
.Select(gg => new
{
State = gg.Key,
FirstTwo = events
// 1
// how to get this clause from variable
//.Where(ee => ee.State == gg.Key)
// 2
// try to take out where expression from query
.Where(_buildExpression(gg.Key))
.Take(2)
})
.ToList();
// method
static Expression<Func<Event, bool>> _buildExpression(string state)
{
return ee => ee.State == state;
}
// exeption
An unhandled exception of type 'System.InvalidOperationException' occurred in EntityFramework.SqlServer.dll
Additional information: variable 'gg' of type 'System.Linq.IGrouping`2[System.String,Entities.Event]' referenced from scope '', but it is not defined
Example of getting where expression from variable, but does not depend on gg.Key (wrong)
Expression<Func<Event, bool>> whereClause = (ee) => (ee.State == "test");
var events = ctx.Events;
var res = events
.GroupBy(ee => ee.State)
.Select(gg => new
{
State = gg.Key,
FirstTwo = events
// 1
// how to get this clause from variable
//.Where(ee => ee.State == gg.Key)
// 2
// try to take out where expression from query
//.Where(_buildExpression(gg.Key))
// 3
// whereClause from variable, but does not depend on gg.Key
.Where(whereClause)
.Take(2)
})
.ToList();
How to take where сlause from variable with depend on gg.Key?
p.s. the query is just example of the problem. The code below does not solve the problem of real query:
var events = ctx.Events;
var res = events
.GroupBy(ee => ee.State)
.Select(gg => new
{
State = gg.Key,
FirstTwo = gg.Take(2)
})
.ToList();
Solution by OP.
Thanks to Ivan Stoev comment.
Expression<Func<Event, string, bool>> whereClause = (ee, state) => (ee.State == state);
var events = ctx.Events;
var res = events
.AsExpandable() // <= add this
.GroupBy(ee => ee.State)
.Select(gg => new
{
State = gg.Key,
FirstTwo = events
.Where(ee => whereClause.Invoke(ee, gg.Key)) // <= Invoke expression
.Take(2)
})
.ToList();
This was made possible by LinqKit