I'm using a LINQ to CRM from Advanced Developer Extension for MS CRM 4.0. It works fine with direct queries. But I've got a problem when query looks like this:
var connectionString = #"User ID=u; Password=p; Authentication Type=AD; Server=http://crm:5555/UO";
var connection = CrmConnection.Parse(connectionString);
var dataContext = new CrmDataContext(connection);
var data = from u in dataContext.Accounts
select new
{
Id = u.AccountID,
Name = u.AccountName,
};
var r = from n in data
where n.Name.StartsWith("test")
select new
{
Id = n.Id
};
r.Dump();
it throws an InvalidOperationException "Cannot determine the attribute name."
It's fine when a condition is directly in first query:
var data = from n in dataContext.Accounts
where n.AccountName.StartsWith("test")
select new
{
Id = n.AccountID,
Name = n.AccountName,
};
I cannot find any useful information about this kind of error. Is it a bug in Xrm Linq Provider?
Thanks in advance for any help.
Try eager loading the initial query with a ToList() so the latter query over your anonymous type is then evaluated locally. I get this is far from ideal if you have a lot of accounts but it'll prove the point. You essentially have a solution anyway in the last statement.
This is because the first query isn't executed at all until you call .Dump() at which point the entire expression including the second query is evaluated as one (deferred execution) by the provider which then looks for an attribute of Name.
Related
I want to get list of records from an entity model (I'm using EF version 5) with a particular accountID. I'm being supplied with the tableName string (this has to be dynamic) and the accountID. I'm trying the following 2 methods but none of them is working (giving me errors on the IQueryable object 'table':
PropertyInfo info = _db.GetType().GetProperty(tableName);
IQueryable table = info.GetValue(_db, null) as IQueryable;
var query = table.Where(t => t.AccountID == accID)
.Select(t => t);
List <object> recList = ( from records in table
where records.AccountID == accID
select records).ToList<object>();
The var query = table.Where(....).Select(...) is the correct move as it allows reflection for the query builder at runtime. However, t.AccountID is an error because of the type of t remains unknown.
I've previously used a similar approach in LINQ to SQL, using System.Linq.Expressions.Expression, e.g.:
// NOT TESTED
var table=context.GetTable(dynamicTableName);
var theT=table.Experssion; // actually, I forget. DynamicExpression or MemberBinding? or
var theField=Expression.Field(theT, "AccountID"); // or dynamic name
var query=table.Where(Expression.Equal(theField, accID);
var recList=query.ToList<object>();
If your object has a common interface there is a simpler syntax:
IQueryable<MyInterface> table = context.GetTable("table") as IQueryable<MyInterface>;
var recList=from r in table
where table.AccountID == ac // if your AccountID is on MyInterface
select table;
If you only have a few tables to support, you could do this as well:
IQueryable<MyInterface> table;
if("table1"==tableName)
table=_db.table1
elseif("table2"==tableName)
table=_db.table2
elseif("table3"==tableName)
table=_db.table3
else
throw exception
I built a DynamicRepository for a project I am working on. It uses generic methods exposed through EF along with dynamic linq. It might be helpful to look at that source code here:
https://dynamicmvc.codeplex.com/SourceControl/latest#DynamicMVC/DynamicMVC/Data/DynamicRepository.cs
You can query the entity framework metadata workspace to get the type for a given table name. This link might help:
Get Tables and Relationships
I am doing some coding in dapper and I get the error No mapping exists from object type to a known managed provider native type this error occurs on the myfriends var for dapper . I am using dapper to get a list of INT values from a table then comparing them against another.. this is the code that gives me that error
int myid = Convert.ToInt32(User.Identity.Name);
// The var myfriend is giving me that error above
var myfriends = sqlConnection.Query<friend>("Select otherfriendsID from friends where profileID=#myidd", new { myidd = myid }).ToList();
var profiles = sqlConnection.Query<profile>("Select top 40 * from profiles where photo is not null AND profileID=#friendship order by profileID desc", new {friendship=myfriends}).ToList();
however if I use entity everything works fine for instance this code below works..
var myfriends = (from s in db.friends where s.profileID == myid select s.otherfriendsID).ToList();
What could be going on here..
myfriends is a List<friend>. You then pass that in as a query parameter, i.e.
new {friendship=myfriends}
with:
AND profileID=#friendship
Now... what is #friendship ? How should it pass in a List<friend> here? What does that even mean to pass in a list of objects (each of which could have multiple properties) as a single parameter? (note: I'm ignoring table-valued-parameters for the purposes of this question)
So: how many myfriends do you expect? 0? 1? any number? This could be, for example:
var profileIds = myfriends.Select(x => x.ProfileId);
...
new {profileIds}
...
AND profileID in #profileIds
or maybe:
new {profileId = myfriends.Single().ProfileId}
...
AND profileID = #profileId
An old question for Linq 2 Entities. I'm just asking it again, in case someone has came up with the solution.
I want to perform query that does this:
UPDATE dbo.Products WHERE Category = 1 SET Category = 5
And I want to do it with Entity Framework 4.3.1.
This is just an example, I have a tons of records I just want 1 column to change value, nothing else. Loading to DbContext with Where(...).Select(...), changing all elements, and then saving with SaveChanges() does not work well for me.
Should I stick with ExecuteCommand and send direct query as it is written above (of course make it reusable) or is there another nice way to do it from Linq 2 Entities / Fluent.
Thanks!
What you are describing isnt actually possible with Entity Framework. You have a few options,
You can write it as a string and execute it via EF with .ExecuteSqlCommand (on the context)
You can use something like Entity Framework Extended (however from what ive seen this doesnt have great performance)
You can update an entity without first fetching it from db like below
using (var context = new DBContext())
{
context.YourEntitySet.Attach(yourExistingEntity);
// Update fields
context.SaveChanges();
}
If you have set-based operations, then SQL is better suited than EF.
So, yes - in this case you should stick with ExecuteCommand.
I don't know if this suits you but you can try creating a stored procedure that will perform the update and then add that procedure to your model as a function import. Then you can perform the update in a single database call:
using(var dc = new YourDataContext())
{
dc.UpdateProductsCategory(1, 5);
}
where UpdateProductsCategory would be the name of the imported stored procedure.
Yes, ExecuteCommand() is definitely the way to do it without fetching all the rows' data and letting ChangeTracker sort it out. Just to provide an example:
Will result in all rows being fetched and an update performed for each row changed:
using (YourDBContext yourDB = new YourDBContext()) {
yourDB.Products.Where(p => p.Category = 1).ToList().ForEach(p => p.Category = 5);
yourDB.SaveChanges();
}
Just a single update:
using (YourDBContext yourDB = new YourDBContext()) {
var sql = "UPDATE dbo.Products WHERE Category = #oldcategory SET Category = #newcategory";
var oldcp = new SqlParameter { ParameterName = "oldcategory", DbType = DbType.Int32, Value = 1 };
var newcp = new SqlParameter { ParameterName = "newcategory", DbType = DbType.Int32, Value = 5 };
yourDB.Database.ExecuteSqlCommand(sql, oldcp, newcp);
}
I have the following Linq query:
var tmp =
from container in Container
join containerType in ContainerType on container.ContainerType equals containerType
where containerType.ContainerTypeID == 2
select new { ContainerID = container.ContainerID, TypeID = container.ContainerTypeID};
var results = tmp.Select((row, index) => new { row.ContainerID, row.TypeID, ContainerIndex = index })
As is, this works fine. If I add the following, so I can see the results in LinqPad, I get the error described in the title of this message:
results.Dump();
This error is not a LinqPad error, it's coming from Linq, and I don't understand what it means.
Thank you.
Okay, I hadn't realised Container was a LINQ to SQL data source to start with. Basically it's failing to convert the second projection to SQL.
So, you want to do just that bit in .NET instead - you can force it to use Enumerable.Select with AsEnumerable:
var results = tmp.AsEnumerable()
.Select((row, index) => new { row.ContainerID, row.TypeID,
ContainerIndex = index });
I have the version 3.0.0.1001 nhibernate.
My objects are basically modeiling a lineup at an event. So I have a StageSet object which represents one slot in the schedule for a stage.
Each StageSet object has a Stage and an Act property.
It also has many Users - people who have favorited the set.
I'm trying to ascertain the most popular sets that have been favorited using the following linq:
var topStars = from s in Db.StageSets
group s by s.Act.Id into g
select new { SetKey = g.Key, Count = g.Count() };
However this just fails with a Could not execute query[SQL: SQL not available] error
Should I be able to do this?
w://
in case someone comes here. The following should work with NH 3.1
var topStars = from s in Db.StageSets
group s by s.Act.Id into g
select new { SetKey = g.First().Act.Id, Count = g.Count() }
You've specified the query correctly in linq. NHibernate is refusing to translate it.
I just copied your query with a slightly different domain and it worked. But that will count StageSets by Act, NOT favorites.