I am trying to convert IQueryable to IEnumerable using SQL query. I am not sure if it's possible.
var id = "123";
string queryString = "SELECT * FROM c WHERE c.ID = " + id;
var dataSource = new List<Book> {
new Book{ ID = "123", Title = "HarryPotter"}}.AsQueryable();
var expected = dataSource.ConvertToIEnumerable(queryString); //IEnumerable type
The dataSource variable has type of IQueryable. Is there any way to pass the queryString variable in order to convert the expected variable has type of IEnumerable?
What you are trying to do is to query List<T> in memory using sql. I do not believe that there is a built-in way in .NET Framework.
What you can do is to use LINQ that provides SQL-like or lambda syntax to collections.
var id = "123";
var dataSource = new List<Book>
{
new Book{ ID = "123", Title = "HarryPotter"}
};
var find = dataSource.Where(i => i.ID == id);
Related
I want to add dynamic expression in linq but facing issues on contains method it is working perfectly for Equal method
Problem is i'm getting FilterField dynamically how to replace in query
So far i had tried
List<int> Ids = new List<int>();
**string filterField ="DEPARTMENT"; ==> Dynamic Field**
var eParam = Expression.Parameter(typeof(EmployeeDetail), "e");
var comparison = Expression.Equal(Expression.Property(eParam, filterField), Expression.Convert(Expression.Constant(Ids), Expression.Property(eParam, filterField).Type));
var lambda = Expression.Lambda<Func<EmployeeDetail, bool>>(comparison, eParam);
var countMonthly1 = ctx.tblMonthlyInput.Join(ctx.tblEmployee, a => a.CompanyId, b => b.CompanyId, (a, b) => b).Where(lambda).Count();
I want to make above query works for Contains method using linq expression
sample query :
var countMonthly = (from a in ctx.tblMonthlyInput
join b in ctx.tblEmployee on a.CompanyId equals b.CompanyId
where categoryId.Contains(a.CategoryId) //want to make this dynamic
select a).Count() == 0;
This will work for you:
void Main()
{
var filterField = "Id";
List<int> Ids = new List<int>();
var eParam = Expression.Parameter(typeof(EmployeeDetail), "e");
var method = Ids.GetType().GetMethod("Contains");
var call = Expression.Call(Expression.Constant(Ids), method, Expression.Property(eParam, filterField));
var lambda = Expression.Lambda<Func<EmployeeDetail, bool>>(call, eParam);
}
public class EmployeeDetail
{
public int Id { get; set; }
}
First, you look for the Contains method on the type of Ids. Then we simply invoke it with Ids as the instance, and the property as the argument
I am trying to query the cosmos and the query works. The query looks like
'Select * from c where c.id IN ('123', '456')'.
Now in my c# code, I get empty result. The c# code looks like :
public void GetValue(IEnumerable<string> ids, string s)
{
StringBuilder sb = new();
_ = sb.Append("SELECT t.id FROM t ")
.Append("WHERE t.id IN (#items) ")
.Append("AND t.state != #state");
var queryDefinition = new QueryDefinition(sb.ToString())
.WithParameter("#items", ids)
.WithParameter("#state", s);
var results = GetQueryResults<TableName>(queryDefinition); // Get Empty Result
// Some logic based on results
}
// GetQueryResults query the container and gets the result for the tableName.
SO, I was able to conclude that the 'IN' query syntax is incorrect. Can anyone help me out.
The problem is here:
.Append("WHERE t.id IN (#items) ")
The list cannot be parameterized. One possiblity is to add the list items as separate parameters. There is an example of that here.
EDIT
I found the solution here
var querySpec = new SqlQuerySpec {
QueryText = "SELECT t.Id FROM t WHERE ARRAY_CONTAINS(#Ids, t.Id)",
Parameters = new SqlParameterCollection {
new SqlParameter {
Name = "#Ids",
Value = ids
}
}
}
I have searching for a while now, but couldn't find how to query from public view. For example, I have predefined public view called Active Accounts and I want data from it.
So far I only know this way, but that not include any views:
using (var xrm = new XrmServiceContext("Xrm"))
{
var activeAccounts = from a in xrm.AccountSet
where a.StateCode == 0
select new { a.Id, a.Name };
// TODO ...
}
But I would like to do it like this (not working, ActiveAccountsView not exist, it's pseudo):
using (var xrm = new XrmServiceContext("Xrm"))
{
var activeAccounts = from a in xrm.ActiveAccountsView
select new { a.Id, a.Name };
// TODO ...
}
Is this even possible?
The query definitions of public views are stored in the savedquery entity, that can be queried using common techniques.
Out-of-the-box views are stored with a fixed ID, so querying Active Accounts on the OrganizationServiceContext object could be done in the following way:
private static IEnumerable<Entity> GetActiveAccounts(OrganizationServiceContext serviceContext)
{
string fetchXml = serviceContext
.CreateQuery("savedquery")
.Where(sq =>
sq.GetAttributeValue<Guid>("savedqueryid") == new Guid("00000000-0000-0000-00AA-000010001002"))
.Select(sq => sq.GetAttributeValue<string>("fetchxml"))
.First();
var request = new RetrieveMultipleRequest
{
Query = new FetchExpression(fetchXml)
};
var response = (RetrieveMultipleResponse) serviceContext.Execute(request);
return response.EntityCollection.Entities;
}
It is not possible to use LINQ here. LINQ relies on the QueryExpression class, but does not implement all its capabilities (OUTER JOIN is a painful omission for example). So, while it is possible to convert a LINQ query to a QueryExpression, the other way around is not.
Paging can be applied by editing the Fetch XML string, but if that is too much hassle, you can also consider to convert the Fetch XML to a QueryExpression and apply paging on that object:
private IEnumerable<Entity> GetActiveAccounts(int pageNumber)
{
string fetchXml = _serviceContext
.CreateQuery("savedquery")
.Where(sq =>
sq.GetAttributeValue<Guid>("savedqueryid") == new Guid("00000000-0000-0000-00AA-000010001002"))
.Select(sq => sq.GetAttributeValue<string>("fetchxml"))
.First();
var conversionRequest = new FetchXmlToQueryExpressionRequest
{
FetchXml = fetchXml
};
var response = (FetchXmlToQueryExpressionResponse)_serviceContext.Execute(conversionRequest);
response.Query.PageInfo = new PagingInfo { Count = 1, PageNumber = pageNumber };
var queryRequest = new RetrieveMultipleRequest
{
Query = response.Query
};
var result = (RetrieveMultipleResponse) _serviceContext.Execute(queryRequest);
return result.EntityCollection.Entities;
}
Additional advantage of the QueryExpression vs. Fetch XML is that it is processed in a bit more efficient way.
The very same can be done with user defined views; these views are stored in the userquery entity. The only difference here is you cannot rely on a fixed view ID. Instead you would need to filter your query on querytype, name, returnedtypecode, ownerid and/or other criteria.
Dynamics CRM also has an OrganizationRequest that allows you to execute the savedquery immediately. However, it returns its result as a resultset XML string, so you would still need to deserialize the response. (A nice example can be found here.) Also, I am not sure if it is possible to limit the result set to a specific page when using the ExecuteByIdSavedQueryRequest:
var request = new ExecuteByIdSavedQueryRequest
{
EntityId = new Guid("00000000-0000-0000-00AA-000010001002")
};
var response = (ExecuteByIdSavedQueryResponse)serviceContext.Execute(request);
string resultset = response.String;
I have Two classes Named OfflineOrderLineItem.cs and OnlineOrderLineItem.cs both have diff Order table named offline and Online
In that i want to Combine the two tables data to search and Display the Fields from both tables
How to do that using linq in mvc4 ??? any idea.....
public virtual IPagedList<OnlineOrderLineItem> SearchOrderLineItems(string PoNumber)
{
var query1 = (from ol in _offlineOrderLineItemRepository.Table
select new
{
ol.Name
}).ToList();
var query2 = (from opv in _onlineOrderLineItemRepository.Table
select new
{
opv.Name
}).ToList();
var finalquery = query1.Union(query2);
if (!String.IsNullOrWhiteSpace(Name))
finalquery = finalquery.Where(c => c.Name == Name);
var orderlineitems = finalquery.ToList(); //its not working it throw a error
return new PagedList<OnlineOrderLineItem>(orderlineitems);//error
}
Error
cannot convert from 'System.Collections.Generic.List<AnonymousType#1>'
to 'System.Linq.IQueryable<Nop.Core.Domain.Management.OnlineOrderLineItem>'
to 'System.Linq.IQueryable<Nop.Core.Domain.Management.OnlineOrderLineItem>'
query1 and query2 are lists of an anonymous type with a single property of type string. (I assmume the ol.Name and opv.Name are strings.) Hence finalQuery and orderlineitems are collections of this anonymous as well. By specifying PagedList<T> you require that the collection passed into the constructor is an enumeration of type T. T is OnlineOrderLineItem, but the enumeration passed into the constructor is the anonymous type which is a different type. Result: compiler error.
To solve the problem I suggest that you define a named helper type that you can use to union the two different types OfflineOrderLineItem and OnlineOrderLineItem:
public class OrderLineItemViewModel
{
public int Id { get; set; }
public string PoNumber { get; set; }
public string Name { get; set; }
// maybe more common properties of `OfflineOrderLineItem`
// and `OnlineOrderLineItem`
}
Then your SearchOrderLineItems method should return a paged list of that helper type:
public virtual IPagedList<OrderLineItemViewModel> SearchOrderLineItems(
string PoNumber)
{
var query1 = from ol in _offlineOrderLineItemRepository.Table
select new OrderLineItemViewModel
{
Id = ol.Id,
PoNumber = ol.PoNumber,
Name = ol.Name,
// maybe more properties
};
// don't use ToList here, so that the later Union and filter
// can be executed in the database
var query2 = from opv in _onlineOrderLineItemRepository.Table
select new OrderLineItemViewModel
{
Id = opv.Id,
PoNumber = opv.PoNumber,
Name = opv.Name,
// maybe more properties
};
// don't use ToList here, so that the later Union and filter
// can be executed in the database
var finalquery = query1.Union(query2);
// again no ToList here
if (!string.IsNullOrWhiteSpace(PoNumber))
finalquery = finalquery.Where(c => c.PoNumber == PoNumber);
var orderlineitems = finalquery.ToList(); // DB query runs here
return new PagedList<OrderLineItemViewModel>(orderlineitems);
}
It is important to use ToList only at the very end of the query. Otherwise you would load the whole tables of all OnlineOrderLineItems and all OfflineOrderLineItems into memory and then filter out the items with the given PoNumber in memory which would be a big overhead and performance desaster.
Instead of
var orderlineitems = finalquery.ToList();
Try
var orderlineitems = finalquery.AsQueryable();
From https://github.com/TroyGoode/PagedList/blob/master/src/PagedList/PagedList.cs, PagedList takes a IQueryable<T>
Queryable.AsQueryable<TElement> Method
I have a database table that contains an nvarchar column like this:
1|12.6|18|19
I have a Business Object that has a Decimal[] property.
My LINQ Query looks like this:
var temp = from r in db.SomeTable select new BusinessObject {
// Other BusinessObject Properties snipped as they are straight 1:1
MeterValues = r.MeterValues.Split('|').Select(Decimal.Parse).ToArray()
};
var result = temp.ToArray();
This throws an NotSupportedException: Method 'System.String[] Split(Char[])' has no supported translation to SQL.
That kinda sucks :) Is there any way I can do this without having to add a string property to the business object or selecting an anonymous type and then iterating through it?
My current "solution" is:
var temp = from r in db.SomeTable select new {
mv = r.MeterValues,
bo = new BusinessObject { // all the other fields }
};
var result = new List<BusinessObject>();
foreach(var t in temp) {
var bo = t.bo;
bo.MeterValues = t.mv.Split('|').Select(Decimal.Parse).ToArray();
result.Add(bo);
}
return result.ToArray(); // The Method returns BusinessObject[]
That's kinda ugly though, with that temporary list.
I've tried adding a let mv = r.MeterValues.Split('|').Select(Decimal.Parse).ToArray() but that essentially leads to the same NotSupportedException.
This is .net 3.5SP1 if that matters.
You need to force the select clause to run on the client by calling .AsEnumerable() first:
var result = db.SomeTable.AsEnumerable().Select(r => new BusinessObject {
...
MeterValues = r.MeterValues.Split('|').Select(Decimal.Parse).ToArray()
}).ToList();
You can't use split, but in this scenario you can do the following:
// Database value is 1|12.6|18|19
string valueToFind = "19";
var temp = from r in db.SomeTable.Where(r => ("|" + r.MeterValues + "|").Contains("|" + valueToFind + "|"));
This code adds outer pipes (|) to the database value on the fly inside the query so you can do start, middle, and end value matches on the string.
For example, the above code looks for "|19|" inside "|1|12.6|18|19|", which is found and valid. This will work for any other valueToFind.
You don't need to use a temporary list:
var query = from r in db.SomeTable
select new
{
r.Id,
r.Name,
r.MeterValues,
...
};
var temp = from x in query.AsEnumerable()
select new BusinessObject
{
Id = x.Id,
Name = x.Name,
MeterValues = x.mv.Split('|').Select(Decimal.Parse).ToArray(),
...
};
return temp.ToArray();
Unfortunately its the IQueryable you are using (Linq to SQL) that is not supporting the Split function.
You are really only left with the IEnumerable (Linq to Objects) support for it in this case. You second code snippet is what you need to do, or something like...
var temp = (from r in db.SomeTable select new {
mv = r.MeterValues,
bo = new BusinessObject { // all the other fields }
}).AsEnumerable().Select(blah, blah) ;