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
Related
I have a List of objects (lst) and DataTable (dt). I want to join the lst and dt on the common field (code as string) and need to return all matching rows in the lst.
My List contains two columns i.e code and name along with values below:
code name
==== ====
1 x
2 y
3 z
The DataTable contains two columns i.e code and value along with values below:
code value
==== =====
3 a
4 b
5 c
The result is:
3 z
Below is my code; but I know it is not a correct statement and thus seeking your advice here. I would be much appreciated if you could guide me on how to write the correct statement.
var ld = from l in lst
join d in dt.AsEnumerable() on l.code equals d.code
select new { l.code, l.name };
You can use Linq query or Join extension method to join the collection on code. Just that when you select data from datatable, you need to use dt.Field method. Please use either of the following code.
Query1:
var ld = lst.Join(dt.AsEnumerable(),
l => l.code,
d => d.Field<string>("code"),
(l, d) => new
{
l.code,
l.name,
value = d.Field<string>("value")
}).ToList();
Query2:
var ld = (from l in lst
join d in dt.AsEnumerable()
on l.code equals d.Field<string>("code")
select new
{
l.code,
l.name,
value = d.Field<string>("value")
}).ToList();
Query3:
var ld = (from l in lst
join d in dt.AsEnumerable()
on l.code equals d.Field<string>("code")
let value = d.Field<string>("value")
select new
{
l.code,
l.name,
value
}).ToList();
You can try any of the below.
var ld = from l in lst
join d in dt.AsEnumerable() on l.code equals d.Field<int>("code")
select new { l.code, l.name };
var ld = lst.Join(dt.AsEnumerable(), l => l.code, d => d.Field<int>("code"), (l,d) => new { l.code, l.name });
It's not clear what your required output is but it looks as if you are correctly getting the only common records. You could extend your select to
select new { l.code, l.name, d.value }
Which would give all the data/columns from both tables.
code name value
==== ==== =====
3 z a
Try this:
var ld = from l in lst
join d in dt.Cast <DataRow>() on l.code equals d["code"].ToString()
select new { l.code, l.name };
SO you have a List and a DataTable. You don't plan to use the Values of the DataTable, only the Codes.
You want to keep those List items, that have a Code that is also a code in the DataTable.
If you plan to use your DataTable for other things than just for this problem, My advice would be to first create a procedure to convert your DataTable into an enumerable sequence.
This way you can add LINQ statements, not only for this problem, but also for other problems.
Let's create an extension method for your DataTable that converts the data into the items that are in the DataTable. See extension methods demystified.
Alas, I don't know what's in your DataTable, let's assume that your DataTable contains Orders
class CustomerOrder
{
public int Id {get; set;}
public int CustomerId {get; set;}
public int Code {get; set;}
public string Value {get; set;}
...
}
The extension method that extends functionality of class DataTable:
public static IEnumerable<Order> ToCustomerOrders(this DataTable table)
{
return table.AsEnumerable().Select(row => new CustomerOrder
{
Id = ...
CustomerId = ...
Code = ...
Value = ...
};
}
I'm not really familiar with DataTables, but you know how to convert the cells of the row into the proper value.
Usage:
DataTable table = ...
Int customerId = 14;
var ordersOfThisCustomer = table.ToCustomerOrders
.Where(customerOrder => customerOrder.CustomerId == customerId)
.FirstOrDefault();
In words: convert the datatable into CustomerOrders, row by row, and check for every converted CustomerOrder whether it has a CustomerId equal to 14. Stop if found. return null if there is no such row.
Now that you've got a nice reusable procedure that is also easy to test, debug and change, we can answer your question.
Given a DataTable with CustomerOrders, and a sequence of items that contain Code and Name, keep only those items from the sequence that have a Code that is also a Code in the DataTable.
var dataTable = ... // your DataTable, filled with CustomerOrders.
var codeNames = ... // your list with Codes and Names
var codesInDataTable = dataTable.ToCustomerOrders
.Select(customerOrder => customerOrder.Code)
.Distinct();
This will create an enumerable sequence that will convert your DataTable row by row and extract property Code. Duplicate Code values will be removed.
If Codes are unique, you don't need Distinct.
Note: the enumerable sequence is not enumerated yet!
var result = codeNames
.Where(codeName => codesInDataTable.Contains(codeName.Code))
.ToList();
In words: for every [Code, Name] combination in your list, keep only those [Code, Name] combinations that have a value for Code that is also in codesInDataTable.
I'm trying to select a distinct values from a DataTable using Linq. The DataTable gets populated from an excel sheet which has dynamic column apart from each excel sheet has a column name SERIAL NUMBER which is mandatory.
I have a DataTable for demo purpose which consist of 4 serial number as:
12345
12345
98765
98765
When I do
var distinctList = dt.AsEnumerable().Select(a => a).Distinct().ToList();
If I do
var distinctList = dt.AsEnumerable().Select(a => a.Field<string>("SERIAL NUMBER").Distinct().ToList();
Then I get the correct results, however but it only contains the one column from dt and not all the other columns
I get all four records instead of 2. Can someone tell me where I'm going wrong please.
The problem is that Distinct method by default uses the default equality comparer, which for DataRow is comparing by reference. To get the desired result, you can use the Distinct overload that allows you to pass IEqualityComparer<T>, and pass DataRowComparer.Default:
The DataRowComparer<TRow> class is used to compare the values of the DataRow objects and does not compare the object references.
var distinctList = dt.AsEnumerable().Distinct(DataRowComparer.Default).ToList();
For more info, see Comparing DataRows (LINQ to DataSet).
So, you want to group them by Serial Number and retrieve the full DataRow? Assuming that after grouping them we want to retrieve the first item:
var distinctList = dt.AsEnumerable().GroupBy(a => a.Field<string>("SERIAL NUMBER"))
.Select(a => a.FirstOrDefault()).Distinct().ToList();
EDIT: As requested
var distinctValues = dt.AsEnumerable().Select(a => a.Field<string>("SERIAL NUMBER")).Distinct().ToList();
var duplicateValues = dt.AsEnumerable().GroupBy(a => a.Field<string>("SERIAL NUMBER")).SelectMany(a => a.Skip(1)).Distinct().ToList();
var duplicatesRemoved = dt.AsEnumerable().Except(duplicateValues);
In ToTable method the first parameter specifies if you want Distinct records, the second specify by which column name we will make distinct.
DataTable returnVals = dt.DefaultView.ToTable(true, "ColumnNameOnWhichYouWantDistinctRecords");
Here there is no need to use linq for this task !
Using Linq a GroupBy would be better suited, by the sounds of it.
var groups = dt.AsEnumerable().GroupBy(a => a.SerialNumber).Select(_ => new {Key = _.Key, Items = _});
This will then contain groupings based on the Serial Number. With each group of items having the same serial number, but other property values different.
Try this:
List<string> distinctValues = (from row in dt.AsEnumerable() select row.Field<string>("SERIAL NUMBER")).Distinct().ToList();
However to me this also works:
List<string> distinctValues = dt.AsEnumerable().Select(row => row.Field<string>("SERIAL NUMBER")).Distinct().ToList();
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")
});
I have a DataTable which I have converted into a list. I would like to know how to query the list and create a new list where the ParentID is null.
DataTable myTable = new DataTable();
myTable.Columns.Add("ParentID", typeof(string));
myTable.Columns.Add("ID", typeof(string));
myTable.Rows.Add(null, "CEO");
myTable.Rows.Add("CEO", "FD");
myTable.Rows.Add("CEO", "CIO");
List<DataRow> lst = myTable.AsEnumerable().ToList();
I am trying something like:
List<DataRow> topNodes = lst.Select("ID is null")
Thanks.
You could try this - search for all cells in a row, for which the content is null. Note that in this case (for the given input - ParentId column is of type string) the row value has to be converted to a string:
// get only those items where ParentId is null
var topRows = myTable
.AsEnumerable()
.ToList()
.Where (row => string.IsNullOrEmpty(row["ParentID"].ToString()))
.ToList();
Output (as List of DataRows) for the given input is:
ParentID | ID
-------------------
null | CEO
try that, assuming you can use LINQ
var topNodes = lst.Where(l => (!(l.ID.HasValue))).ToList();
Edit:
I see your ID is String, so it should be like that:
var topNodes = lst.Where(l => ID.IsNullOrEmpty()).ToList();
Edit:
The list is DataRow so:
var topNodes = lst.Where(row => row["ID"].IsNullOrEmpty()).ToList();
Edit:
You added more information regarding what you want to do. If all you need is list or DataRow, I would filter first and then cast to list:
var topNodes = myTable.Select("ID is null").AsEnumerable().ToList();
Note: See comments under original post.
List<DataRow> lst = myTable.Select("ParentID is null").ToList();
Edit: I see that my answer is very similar to Kris Ivanov's but mine is a bit simpler and doesn't use the noxious var keyword and I suggested using Table.Select first in the comments. So, I'll leave it be.
I have a List and a DataTable which contains a column to match the IDs in the list. I need to identify all IDs in my list that are not in the DataTable. I tried getting an IEnumberable DataRow and joining that to the list but I'm not able to identify the missing ones.
Here is my code and what I've tried...
List<int> JobIdList = (from i in EntryItems select i.JobID.Value).ToList<int>();
IEnumerable<DataRow> rowInfo = JobBLL.JobsExist(JobIdList).AsEnumerable();
var MissingList = (from rec in rowInfo
join id in JobIdList
on rec.Field<int>("JobID") equals id
into grouping
from id in grouping.DefaultIfEmpty()
select new { id }).ToList();
if (MissingList.Count > 0) { // Show message and exit }
The problem is that this returns the items in the data table that ARE found. Let's say I have 1, 2, and 3 in my list but my data table only has 1 and 3. I want to have 2 in MissingList.
Any thoughts?
var jobIdList = new HashSet<int>(from i in EntryItems select i.JobID.Value);
var rows = JobBLL.JobsExist(jobIdList).AsEnumerable();
var foundIds = (from x in rows select x.Field<int>("JobID")).ToList();
var missingIds = jobIdList.Except(foundIds);
You need to add the below line of code into your code.
var missingIds = JobIdList.Except(MissingList);