I wrote the following query in LINQ:
memberlist is List of membershipuserwrapper
List<usercodes> testlist = new List<usercodes>();
testlist.Add(new usercodes { usercode = "na02\\srosner" });
testlist.Add(new usercodes { usercode = "Schie#testtest.com" });
var filtered = (from c in memberList
where (from t in testlist
select t.usercode.ToLower())
.Contains(c.UserName.ToLower())
select c)
.ToList();
Now, I have DataTable with a list of users in place of testlist and I want to use that DataTable in place of my LINQ query.
Can I use that how to do that in way of DataTable?
You should be able to use:
from t in testlist.AsEnumerable()
select t.Field<string>("usercode").ToLower()
in place of the original:
from t in testlist
select t.usercode.ToLower()
Personally, though, I'd say that the List<usercodes> is a vast improvement from a DataTable, and would encourage you to pursue the original version (maybe changing the class-name to UserCodes or similar).
Related
I am using Linq to Sql and I need to fetch only the needed fields. This is something that I was able to accomplish using Dynamic Linq. Does anyone know how I can fetch only one or more fields and then add it to my Grid without re query and regenerate the whole object again?? Something similar to Merge method of a dataset but with Linq to SQL?
I hope I understand your question. Does one of these help you?
var List1 = db.myTable.Select(k => new myObject
{
ID = k.Id,
field1 = k.field1
});
var List2 = from k in db.myTable select new myObject()
{
ID = k.Id,
field1 = k.field1
};
else can you provide an example?
I have a linq query which is giving me desired output :
var data = (from c in dtskip.AsEnumerable()
select new[] {
c.Field<string>("Suburb"), c.Field<string>("Postcode"), c.Field<string>("State"),c.Field<string>("ID"), c.Field<string>("SEARCHKEY"), c.Field<string>("RATING"), c.Field<string>("DELIVERY")
});
How can i select all the column instead of giving name like c.field<string>("postcode") .My output is the data only from datatable dtskip :
output:
["DARWIN","0800","NT","2","DARWINNT","A","Delivery Area"]
,["ALAWA","0810","NT","5","ALAWANT","A","Delivery Area"],
["BRINKIN","0810","NT","6","BRINKINNT","A","Delivery Area"],
is there any other way i can get the output in dis way from datatable using linq query .
DataRow contains an ItemArray member which returns all the data in that row as an array, the downside is they are all returned as objects but if all your columns are the same type you can cast the ItemArray in line to the desired type (in this case string)
dtskip.Rows.Cast<DataRow>().Select(r => r.ItemArray.Cast<string>());
This will give you an IEnumerable<IEnumerable<string>> to work with.
have you tried
var data = (From c in dtskip
select c).AsEnumerable(); //Not sure about the AsEnumerable :s
Are you looking for something like this?
var data = dtskip.AsEnumerable().
Select(x => new
{
Suburb = x.Field<string>("Suburb"),
Postcode= x.Field<string>("Postcode"),
State= x.Field<string>("State"),
Id= x.Field<string>("ID"),
Searchkey = x.Field<string>("SEARCHKEY"),
Rating = x.Field<string>("RATING"),
Delivery = x.Field<string>("DELIVERY")
});
IEnumerable<classB> list = getItems();
//dt is datatable
list = list.Where(x => Convert.ToInt32( !dt.Columns["Id"]) == (x.Id));
I want to only keep the items in the list which match in datatable id column. The rest are removed. I m not doing it right.
The datatable can have: ID - 1,3,4,5,7
The list can have: ID - 1,2,3,4,5,6,7,8,9,10
I want the output list to have: ID - 1,3,4,5,7
Your code won't work because you're comparing a definition of a column to an integer value. That's not a sensible comparison to make.
What you can do is put all of the values from the data table into a collection that can be effectively searched and then get all of the items in the list that are also in that collection:
var ids = new HashSet<int>(dt.AsEnumerable()
.Select(row => row.Field<int>("Id"));
list = list.Where(x => ids.Contains(x.Id));
Try this one
var idList = dt.AsEnumerable().Select(d => (int) d["Id"]).ToList();
list = list.Where(x => idList.Contains(x.Id));
You can't do it like that. Your dt.Columns["Id"] returns the DataColumn and not the value inside that column in a specific datarow. You need to make a join between two linq query, the first one you already have, the other you need to get from the DataTable.
var queryDt = (from dtRow in dt
where !dtRow.IsNull("Id")
select int.Parse(dtRow["Id"])).ToList();
Now the join
var qry = from nonNull in queryDt
join existing in list on nonNull equals list.id
I have the following list keyvaluepair
var countryList = new List<KeyValuePair<string,int>>();
which I then populate with a while loop from the db something like this
countryList.Add(new KeyValuePair<string, int>("cname",1));
I then want to query it using linq and order it at the same time, I have this
var lst = from s in countryList
orderby s.[0]
select s;
As you can guess it doesn't work, I know why it's the s.[0] but can someone tell me what the correct syntax is?
thanks
I would make it in a one line instead
var sortedCountryList = countryList.OrderBy(s=>s.Key);
and if you only want the country names in a list
var sortedCountryList = countryList.OrderBy(s=>s.Key).Select(s=>s.Value);
var lst = from s in countryList
orderby s.Key
select s;
I need to retrieve a list of entities from my database that matches a list of items in a plain list (not EF). Is this possible with Entity Framework 4.1?
Example:
var list = new List<string> { "abc", "def", "ghi" };
var items = from i in context.Items
where list.Contains(i.Name)
select i;
This works great to return rows that match one property, but I actually have a more complex property:
var list = new List<Tuple<string, string>>
{
new Tuple<string,string>("abc", "123"),
new Tuple<string,string>("def", "456")
};
// i need to write a query something like this:
var items = from i in context.Items
where list.Contains(new Tuple<string,string>(i.Name, i.Type))
select i;
I know that is not valid because it will say it needs to be a primitive type, but is there any way to do what I'm trying to accomplish or will I need to resort to a stored procedure?
You have a few options:
1) You could, of course, write a stored procedure to do what you need and call it.
2) You could read the table into memory and then query the in memory list...that way you don't have to use primitives:
var items = from i in context.Items.ToList()
where list.Contains(new Tuple<string, string>(i.Name, i.Type))
select i;
3) You could also convert your query to use primitives to achieve the same goal:
var items = from i in context.Items
join l in list
on new { i.Name, i.Type } equals
new { Name = l.Item1, Type = l.Item2 }
select i;
I would go with the second option as long as the table isn't extremely large. Otherwise, go with the first.
You need to break it down to sub-properties. For example, something like (this might not compile, i'm not able to test at the moment, but it should give you something to work with):
var items = from i in context.Items
where list.Select(x => x.Item1).Contains(i.Name)
&& list.Select(x => x.Item2).Contains(i.Type)
select i;
You have to think about what the resulting SQL would look like, this would be difficult to do directly in SQL.
My suggestion would be you split out one field of the tuples and use this to cut down the results list, get back the query result then filter again to match one of the tuples e.g.
var list = new List<string> { "abc", "def" };
var list2 = new List<Tuple<string, string>>
{
new Tuple<string,string>("abc", "123"),
new Tuple<string,string>("def", "456")
};
var items = (from i in context.Items
where list.Contains(i.Name)
select i)
.AsEnumerable()
.Where(i => list2.Any(j => j.val1 == i.Name && j.val2 == i.Type);