At the risk of asking a duplicate question, I cannot seem to get this to work. There are many examples of what I want to do but the syntax isnt quite the same and nothing has worked. I am teaching myself Linq. This query gets a list of ids from SQL server. Without the "ToString()" it says "cant convert GUID to string[]". Please advise and thanks in advance.
public string[] GetAllRoleIDs(string param)
{
using (DBEntities de = new DBEntities())
{
string[] roleset = (from p in de.MySQLView
where p.anotherfield == param
select p.RoleID.ToString()).Distinct().ToArray();
return roleset;
}
}
You want AsEnumerable() to force the ToString() call to be evaluated locally rather than as part of the EF query. For example:
using (DBEntities de = new DBEntities())
{
string[] roleset = de.MySQLView
.Where(p => p.anotherfield == param)
.Select(p => p.RoleID)
.Distinct()
.AsEnumerable()
.Select(guid => guid.ToString())
.ToArray();
return roleset;
}
(I've converted it from a query expression to use dot notation just because mixing and matching between the two is cumbersome, and you've only got a where and a select. You can use a query expression if you like, of course.)
Related
I'm getting the following error when trying to do a linq query:
LINQ to Entities does not recognize the method 'Boolean
IsCharityMatching(System.String, System.String)' method, and this
method cannot be translated into a store expression.
I've read lots of previous questions where people get the same error, and if I understand this correctly it's because LINQ to Entities requires the whole linq query expression to be translated to a server query, and therefore you can't call an outside method in it. I haven't been able to convert my scenario into something that works yet, and my brain is starting to melt down, so I was hoping someone could point me in the right direction. We're using Entity Framework and the specification pattern (and I'm new to both).
Here's the code that uses the specification:
ISpecification<Charity> specification = new CharitySearchSpecification(charityTitle, charityReference);
charities = charitiesRepository.Find(specification).OrderBy(p => p.RegisteredName).ToList();
Here's the linq expression:
public System.Linq.Expressions.Expression<Func<Charity, bool>> IsSatisfied()
{
return p => p.IsCharityMatching(this.charityName, this.charityReference);
}
Here's the IsCharityMatching method:
public bool IsCharityMatching(string name, string referenceNumber)
{
bool exists = true;
if (!String.IsNullOrEmpty(name))
{
if (!this.registeredName.ToLower().Contains(name.ToLower()) &&
!this.alias.ToLower().Contains(name.ToLower()) &&
!this.charityId.ToLower().Contains(name.ToLower()))
{
exists = false;
}
}
if (!String.IsNullOrEmpty(referenceNumber))
{
if (!this.charityReference.ToLower().Contains(referenceNumber.ToLower()))
{
exists = false;
}
}
return exists;
}
Let me know if you need any more information.
Many thanks,
Annelie
As you've figured out, Entity Framework can't actually run your C# code as part of its query. It has to be able to convert the query to an actual SQL statement. In order for that to work, you will have to restructure your query expression into an expression that Entity Framework can handle.
public System.Linq.Expressions.Expression<Func<Charity, bool>> IsSatisfied()
{
string name = this.charityName;
string referenceNumber = this.referenceNumber;
return p =>
(string.IsNullOrEmpty(name) ||
p.registeredName.ToLower().Contains(name.ToLower()) ||
p.alias.ToLower().Contains(name.ToLower()) ||
p.charityId.ToLower().Contains(name.ToLower())) &&
(string.IsNullOrEmpty(referenceNumber) ||
p.charityReference.ToLower().Contains(referenceNumber.ToLower()));
}
I got the same error in this code:
var articulos_en_almacen = xx.IV00102.Where(iv => alm_x_suc.Exists(axs => axs.almacen == iv.LOCNCODE.Trim())).Select(iv => iv.ITEMNMBR.Trim()).ToList();
this was the exactly error:
System.NotSupportedException: 'LINQ to Entities does not recognize the method 'Boolean Exists(System.Predicate`1[conector_gp.Models.almacenes_por_sucursal])' method, and this method cannot be translated into a store expression.'
I solved this way:
var articulos_en_almacen = xx.IV00102.ToList().Where(iv => alm_x_suc.Exists(axs => axs.almacen == iv.LOCNCODE.Trim())).Select(iv => iv.ITEMNMBR.Trim()).ToList();
I added a .ToList() before my table, this decouple the Entity and linq code, and avoid my next linq expression be translated
NOTE: this solution isn't optimal, because avoid entity filtering, and simply loads all table into memory
I ran into the same problem today, this was the first link I hit. However I was not looking for verifying my query. So if somebody else has the same issue and are looking for this solution it is added here. My issue was in another link.
It is the most common exception occurs when working with entity framework and converting data inside IQueryable result for filtering.
using (var context = new CustomerContext())
{
var item = context.InvoiceItems
.Where(i => i.Code == code.ToString())
.FirstOrDefault();
}
Several solutions exist. Move ToString() call to a separate line.
using (var context = new CustomerContext())
{
string codeStr = code.ToString();
var item = context.InvoiceItems
.Where(i => i.Code == codeStr)
.FirstOrDefault();
}
Use EF Extension Method,
using (var context = new CustomerContext())
{
var item = context.InvoiceItems
.Where(i => i.Code == SqlFunctions.StringConvert(code))
.FirstOrDefault();
}
Convert IQueryable result to IEnumerable before Filtering
using (var context = new CustomerContext())
{
var item = context.InvoiceItems.AsEnumerable()
.Where(i => i.Code == code.ToString())
.FirstOrDefault();
}
If anyone is looking for a VB.Net answer (as I was initially), here it is:
Public Function IsSatisfied() As Expression(Of Func(Of Charity, String, String, Boolean))
Return Function(charity, name, referenceNumber) (String.IsNullOrWhiteSpace(name) Or
charity.registeredName.ToLower().Contains(name.ToLower()) Or
charity.alias.ToLower().Contains(name.ToLower()) Or
charity.charityId.ToLower().Contains(name.ToLower())) And
(String.IsNullOrEmpty(referenceNumber) Or
charity.charityReference.ToLower().Contains(referenceNumber.ToLower()))
End Function
I got the same error in this code:
Solution
IQueryable to .toList() is the best option
Hi I i'm doing this linq expression in an web api but then it gives this error
LINQ to Entities does not recognize the method 'WebApplicationAPI.Models.Registo convertToRegisto(WebApplicationAPI.Models.TBS0017)' method, and this method cannot be translated into a store expression.
Here's the code:
var tBS0017 = from row in db.TBS0017
where row.Cartao == cartao && row.Data == data
var teste = tBS0017.Select(x => convertToRegisto(x));
public Registo convertToRegisto(TBS0017 x)
{
string term = db.ba_terminal.Where(y => "00"+y.terminal_id.ToString() == x.CodTerminal).Select(y => y.terminal_name).ToString();
string emp = db.TG0006.Where(y => "00"+y.IdCompanhia.ToString() == x.IdCompanhia.ToString()).Select(y => y.DsCompanhia).ToString();
Registo r = new Registo() { Cartao = x.Cartao, Data = x.Data, Hora = x.Hora, Local = term, Empresa = emp };
return r;
}
Bring tBS0017 back into memory with ToList()
var results = tBS0017.ToList()
.Select(x => convertToRegisto(x));
However, this has some serious flaws.
For every element in tBS0017, you are doing 2 more db query's. You should really be doing this in the one query and projecting to Registo
The issue is that using Linq to Entities tries to convert your C# code into equivalent SQL which can run your query. There is no function "convertToRegisto" in SQL so this gives you an exception.
You can solve the issue by using ToList() to bring the result of the query into memory first. Then you're able to use your methods in the Select.
var teste = tBS0017
.ToList()
.Select(x => convertToRegisto(x));
You can not convert int value from linq to sql. You must use the sql function that convert int to string values. On the other hand, in memory handling is quite heavy operation
e.g
string term = db.ba_terminal.Where(y => "00"+
SqlFunctions.StringConvert((double)y.terminal_id) ==
x.CodTerminal).Select(y => y.terminal_name).ToString();
I'm getting the following error when trying to do a linq query:
LINQ to Entities does not recognize the method 'Boolean
IsCharityMatching(System.String, System.String)' method, and this
method cannot be translated into a store expression.
I've read lots of previous questions where people get the same error, and if I understand this correctly it's because LINQ to Entities requires the whole linq query expression to be translated to a server query, and therefore you can't call an outside method in it. I haven't been able to convert my scenario into something that works yet, and my brain is starting to melt down, so I was hoping someone could point me in the right direction. We're using Entity Framework and the specification pattern (and I'm new to both).
Here's the code that uses the specification:
ISpecification<Charity> specification = new CharitySearchSpecification(charityTitle, charityReference);
charities = charitiesRepository.Find(specification).OrderBy(p => p.RegisteredName).ToList();
Here's the linq expression:
public System.Linq.Expressions.Expression<Func<Charity, bool>> IsSatisfied()
{
return p => p.IsCharityMatching(this.charityName, this.charityReference);
}
Here's the IsCharityMatching method:
public bool IsCharityMatching(string name, string referenceNumber)
{
bool exists = true;
if (!String.IsNullOrEmpty(name))
{
if (!this.registeredName.ToLower().Contains(name.ToLower()) &&
!this.alias.ToLower().Contains(name.ToLower()) &&
!this.charityId.ToLower().Contains(name.ToLower()))
{
exists = false;
}
}
if (!String.IsNullOrEmpty(referenceNumber))
{
if (!this.charityReference.ToLower().Contains(referenceNumber.ToLower()))
{
exists = false;
}
}
return exists;
}
Let me know if you need any more information.
Many thanks,
Annelie
As you've figured out, Entity Framework can't actually run your C# code as part of its query. It has to be able to convert the query to an actual SQL statement. In order for that to work, you will have to restructure your query expression into an expression that Entity Framework can handle.
public System.Linq.Expressions.Expression<Func<Charity, bool>> IsSatisfied()
{
string name = this.charityName;
string referenceNumber = this.referenceNumber;
return p =>
(string.IsNullOrEmpty(name) ||
p.registeredName.ToLower().Contains(name.ToLower()) ||
p.alias.ToLower().Contains(name.ToLower()) ||
p.charityId.ToLower().Contains(name.ToLower())) &&
(string.IsNullOrEmpty(referenceNumber) ||
p.charityReference.ToLower().Contains(referenceNumber.ToLower()));
}
I got the same error in this code:
var articulos_en_almacen = xx.IV00102.Where(iv => alm_x_suc.Exists(axs => axs.almacen == iv.LOCNCODE.Trim())).Select(iv => iv.ITEMNMBR.Trim()).ToList();
this was the exactly error:
System.NotSupportedException: 'LINQ to Entities does not recognize the method 'Boolean Exists(System.Predicate`1[conector_gp.Models.almacenes_por_sucursal])' method, and this method cannot be translated into a store expression.'
I solved this way:
var articulos_en_almacen = xx.IV00102.ToList().Where(iv => alm_x_suc.Exists(axs => axs.almacen == iv.LOCNCODE.Trim())).Select(iv => iv.ITEMNMBR.Trim()).ToList();
I added a .ToList() before my table, this decouple the Entity and linq code, and avoid my next linq expression be translated
NOTE: this solution isn't optimal, because avoid entity filtering, and simply loads all table into memory
I ran into the same problem today, this was the first link I hit. However I was not looking for verifying my query. So if somebody else has the same issue and are looking for this solution it is added here. My issue was in another link.
It is the most common exception occurs when working with entity framework and converting data inside IQueryable result for filtering.
using (var context = new CustomerContext())
{
var item = context.InvoiceItems
.Where(i => i.Code == code.ToString())
.FirstOrDefault();
}
Several solutions exist. Move ToString() call to a separate line.
using (var context = new CustomerContext())
{
string codeStr = code.ToString();
var item = context.InvoiceItems
.Where(i => i.Code == codeStr)
.FirstOrDefault();
}
Use EF Extension Method,
using (var context = new CustomerContext())
{
var item = context.InvoiceItems
.Where(i => i.Code == SqlFunctions.StringConvert(code))
.FirstOrDefault();
}
Convert IQueryable result to IEnumerable before Filtering
using (var context = new CustomerContext())
{
var item = context.InvoiceItems.AsEnumerable()
.Where(i => i.Code == code.ToString())
.FirstOrDefault();
}
If anyone is looking for a VB.Net answer (as I was initially), here it is:
Public Function IsSatisfied() As Expression(Of Func(Of Charity, String, String, Boolean))
Return Function(charity, name, referenceNumber) (String.IsNullOrWhiteSpace(name) Or
charity.registeredName.ToLower().Contains(name.ToLower()) Or
charity.alias.ToLower().Contains(name.ToLower()) Or
charity.charityId.ToLower().Contains(name.ToLower())) And
(String.IsNullOrEmpty(referenceNumber) Or
charity.charityReference.ToLower().Contains(referenceNumber.ToLower()))
End Function
I got the same error in this code:
Solution
IQueryable to .toList() is the best option
I'm getting the following error when trying to do a linq query:
LINQ to Entities does not recognize the method 'Boolean
IsCharityMatching(System.String, System.String)' method, and this
method cannot be translated into a store expression.
I've read lots of previous questions where people get the same error, and if I understand this correctly it's because LINQ to Entities requires the whole linq query expression to be translated to a server query, and therefore you can't call an outside method in it. I haven't been able to convert my scenario into something that works yet, and my brain is starting to melt down, so I was hoping someone could point me in the right direction. We're using Entity Framework and the specification pattern (and I'm new to both).
Here's the code that uses the specification:
ISpecification<Charity> specification = new CharitySearchSpecification(charityTitle, charityReference);
charities = charitiesRepository.Find(specification).OrderBy(p => p.RegisteredName).ToList();
Here's the linq expression:
public System.Linq.Expressions.Expression<Func<Charity, bool>> IsSatisfied()
{
return p => p.IsCharityMatching(this.charityName, this.charityReference);
}
Here's the IsCharityMatching method:
public bool IsCharityMatching(string name, string referenceNumber)
{
bool exists = true;
if (!String.IsNullOrEmpty(name))
{
if (!this.registeredName.ToLower().Contains(name.ToLower()) &&
!this.alias.ToLower().Contains(name.ToLower()) &&
!this.charityId.ToLower().Contains(name.ToLower()))
{
exists = false;
}
}
if (!String.IsNullOrEmpty(referenceNumber))
{
if (!this.charityReference.ToLower().Contains(referenceNumber.ToLower()))
{
exists = false;
}
}
return exists;
}
Let me know if you need any more information.
Many thanks,
Annelie
As you've figured out, Entity Framework can't actually run your C# code as part of its query. It has to be able to convert the query to an actual SQL statement. In order for that to work, you will have to restructure your query expression into an expression that Entity Framework can handle.
public System.Linq.Expressions.Expression<Func<Charity, bool>> IsSatisfied()
{
string name = this.charityName;
string referenceNumber = this.referenceNumber;
return p =>
(string.IsNullOrEmpty(name) ||
p.registeredName.ToLower().Contains(name.ToLower()) ||
p.alias.ToLower().Contains(name.ToLower()) ||
p.charityId.ToLower().Contains(name.ToLower())) &&
(string.IsNullOrEmpty(referenceNumber) ||
p.charityReference.ToLower().Contains(referenceNumber.ToLower()));
}
I got the same error in this code:
var articulos_en_almacen = xx.IV00102.Where(iv => alm_x_suc.Exists(axs => axs.almacen == iv.LOCNCODE.Trim())).Select(iv => iv.ITEMNMBR.Trim()).ToList();
this was the exactly error:
System.NotSupportedException: 'LINQ to Entities does not recognize the method 'Boolean Exists(System.Predicate`1[conector_gp.Models.almacenes_por_sucursal])' method, and this method cannot be translated into a store expression.'
I solved this way:
var articulos_en_almacen = xx.IV00102.ToList().Where(iv => alm_x_suc.Exists(axs => axs.almacen == iv.LOCNCODE.Trim())).Select(iv => iv.ITEMNMBR.Trim()).ToList();
I added a .ToList() before my table, this decouple the Entity and linq code, and avoid my next linq expression be translated
NOTE: this solution isn't optimal, because avoid entity filtering, and simply loads all table into memory
I ran into the same problem today, this was the first link I hit. However I was not looking for verifying my query. So if somebody else has the same issue and are looking for this solution it is added here. My issue was in another link.
It is the most common exception occurs when working with entity framework and converting data inside IQueryable result for filtering.
using (var context = new CustomerContext())
{
var item = context.InvoiceItems
.Where(i => i.Code == code.ToString())
.FirstOrDefault();
}
Several solutions exist. Move ToString() call to a separate line.
using (var context = new CustomerContext())
{
string codeStr = code.ToString();
var item = context.InvoiceItems
.Where(i => i.Code == codeStr)
.FirstOrDefault();
}
Use EF Extension Method,
using (var context = new CustomerContext())
{
var item = context.InvoiceItems
.Where(i => i.Code == SqlFunctions.StringConvert(code))
.FirstOrDefault();
}
Convert IQueryable result to IEnumerable before Filtering
using (var context = new CustomerContext())
{
var item = context.InvoiceItems.AsEnumerable()
.Where(i => i.Code == code.ToString())
.FirstOrDefault();
}
If anyone is looking for a VB.Net answer (as I was initially), here it is:
Public Function IsSatisfied() As Expression(Of Func(Of Charity, String, String, Boolean))
Return Function(charity, name, referenceNumber) (String.IsNullOrWhiteSpace(name) Or
charity.registeredName.ToLower().Contains(name.ToLower()) Or
charity.alias.ToLower().Contains(name.ToLower()) Or
charity.charityId.ToLower().Contains(name.ToLower())) And
(String.IsNullOrEmpty(referenceNumber) Or
charity.charityReference.ToLower().Contains(referenceNumber.ToLower()))
End Function
I got the same error in this code:
Solution
IQueryable to .toList() is the best option
I'm migrating some stuff from one mysql server to a sql server but i can't figure out how to make this code work:
using (var context = new Context())
{
...
foreach (var item in collection)
{
IQueryable<entity> pages = from p in context.pages
where p.Serial == item.Key.ToString()
select p;
foreach (var page in pages)
{
DataManager.AddPageToDocument(page, item.Value);
}
}
Console.WriteLine("Done!");
Console.Read();
}
When it enters into the second foreach (var page in pages) it throws an exception saying:
LINQ to Entities does not recognize the method 'System.String
ToString()' method, and this method cannot be translated into a store
expression.
Anyone know why this happens?
Just save the string to a temp variable and then use that in your expression:
var strItem = item.Key.ToString();
IQueryable<entity> pages = from p in context.pages
where p.Serial == strItem
select p;
The problem arises because ToString() isn't really executed, it is turned into a MethodGroup and then parsed and translated to SQL. Since there is no ToString() equivalent, the expression fails.
Note:
Make sure you also check out Alex's answer regarding the SqlFunctions helper class that was added later. In many cases it can eliminate the need for the temporary variable.
As others have answered, this breaks because .ToString fails to translate to relevant SQL on the way into the database.
However, Microsoft provides the SqlFunctions class that is a collection of methods that can be used in situations like this.
For this case, what you are looking for here is SqlFunctions.StringConvert:
from p in context.pages
where p.Serial == SqlFunctions.StringConvert((double)item.Key.Id)
select p;
Good when the solution with temporary variables is not desirable for whatever reasons.
Similar to SqlFunctions you also have the EntityFunctions (with EF6 obsoleted by DbFunctions) that provides a different set of functions that also are data source agnostic (not limited to e.g. SQL).
The problem is that you are calling ToString in a LINQ to Entities query. That means the parser is trying to convert the ToString call into its equivalent SQL (which isn't possible...hence the exception).
All you have to do is move the ToString call to a separate line:
var keyString = item.Key.ToString();
var pages = from p in context.entities
where p.Serial == keyString
select p;
Cast table to Enumerable, then you call LINQ methods with using ToString() method inside:
var example = contex.table_name.AsEnumerable()
.Select(x => new {Date = x.date.ToString("M/d/yyyy")...)
But be careful, when you calling AsEnumerable or ToList methods because you will request all data from all entity before this method. In my case above I read all table_name rows by one request.
Had a similar problem.
Solved it by calling ToList() on the entity collection and querying the list.
If the collection is small this is an option.
IQueryable<entity> pages = context.pages.ToList().Where(p=>p.serial == item.Key.ToString())
Hope this helps.
Upgrading to Entity Framework Version 6.2.0 worked for me.
I was previously on Version 6.0.0.
Hope this helps,
Change it like this and it should work:
var key = item.Key.ToString();
IQueryable<entity> pages = from p in context.pages
where p.Serial == key
select p;
The reason why the exception is not thrown in the line the LINQ query is declared but in the line of the foreach is the deferred execution feature, i.e. the LINQ query is not executed until you try to access the result. And this happens in the foreach and not earlier.
If you really want to type ToString inside your query, you could write an expression tree visitor that rewrites the call to ToString with a call to the appropriate StringConvert function:
using System.Linq;
using System.Data.Entity.SqlServer;
using System.Linq.Expressions;
using static System.Linq.Expressions.Expression;
using System;
namespace ToStringRewriting {
class ToStringRewriter : ExpressionVisitor {
static MethodInfo stringConvertMethodInfo = typeof(SqlFunctions).GetMethods()
.Single(x => x.Name == "StringConvert" && x.GetParameters()[0].ParameterType == typeof(decimal?));
protected override Expression VisitMethodCall(MethodCallExpression node) {
var method = node.Method;
if (method.Name=="ToString") {
if (node.Object.GetType() == typeof(string)) { return node.Object; }
node = Call(stringConvertMethodInfo, Convert(node.Object, typeof(decimal?));
}
return base.VisitMethodCall(node);
}
}
class Person {
string Name { get; set; }
long SocialSecurityNumber { get; set; }
}
class Program {
void Main() {
Expression<Func<Person, Boolean>> expr = x => x.ToString().Length > 1;
var rewriter = new ToStringRewriter();
var finalExpression = rewriter.Visit(expr);
var dcx = new MyDataContext();
var query = dcx.Persons.Where(finalExpression);
}
}
}
In MVC, assume you are searching record(s) based on your requirement or information.
It is working properly.
[HttpPost]
[ActionName("Index")]
public ActionResult SearchRecord(FormCollection formcollection)
{
EmployeeContext employeeContext = new EmployeeContext();
string searchby=formcollection["SearchBy"];
string value=formcollection["Value"];
if (formcollection["SearchBy"] == "Gender")
{
List<MvcApplication1.Models.Employee> emplist = employeeContext.Employees.Where(x => x.Gender == value).ToList();
return View("Index", emplist);
}
else
{
List<MvcApplication1.Models.Employee> emplist = employeeContext.Employees.Where(x => x.Name == value).ToList();
return View("Index", emplist);
}
}
I got the same error in this case:
var result = Db.SystemLog
.Where(log =>
eventTypeValues.Contains(log.EventType)
&& (
search.Contains(log.Id.ToString())
|| log.Message.Contains(search)
|| log.PayLoad.Contains(search)
|| log.Timestamp.ToString(CultureInfo.CurrentUICulture).Contains(search)
)
)
.OrderByDescending(log => log.Id)
.Select(r => r);
After spending way too much time debugging, I figured out that error appeared in the logic expression.
The first line search.Contains(log.Id.ToString()) does work fine, but the last line that deals with a DateTime object made it fail miserably:
|| log.Timestamp.ToString(CultureInfo.CurrentUICulture).Contains(search)
Remove the problematic line and problem solved.
I do not fully understand why, but it seems as ToString() is a LINQ expression for strings, but not for Entities. LINQ for Entities deals with database queries like SQL, and SQL has no notion of ToString(). As such, we can not throw ToString() into a .Where() clause.
But how then does the first line work? Instead of ToString(), SQL have CAST and CONVERT, so my best guess so far is that linq for entities uses that in some simple cases. DateTime objects are not always found to be so simple...
My problem was that I had a 'text' data type for this column (due to a migration from sqlite).
Solution: just change the data type to 'nvarchar()' and regenerate the table.
Then Linq accepts the string comparison.
I am working on retiring Telerik Open Access and replacing it with Entity Framework 4.0. I came across same issue that telerik:GridBoundColumn filtering stopped working.
I find out that its not working only on System.String DataTypes. So I found this thread and solved it by just using .List() at the end of my Linq query as follows:
var x = (from y in db.Tables
orderby y.ColumnId descending
select new
{
y.FileName,
y.FileSource,
y.FileType,
FileDepartment = "Claims"
}).ToList();
Just turn the LINQ to Entity query into a LINQ to Objects query (e.g. call ToArray) anytime you need to use a method call in your LINQ query.