I'm selecting some data from table A with a column value and type which have relationship with table B where there is a column coef that contains (-1,0,1)
When retrieving from A I want to multiply the value with coef.
Something like this?
var result = from a in tableA
join b in tableB on a.Key = b.ForeignKey
select new
{
Value = a.value * b.coef
};
You could use a LINQ expression to do it in one line:
dt.Rows.ForEach(x => x["value"] = (double)x["value"] * (double)x["coef"]);
or you could just add another column to the DataTable:
dt.Columns.Add("Result", typeof(decimal));
dt["result"] = "value * coef";
Related
I have a DataTable, with two columns of type String named ID and Value. These values are not required to be unique.
As I add to my DataTable throughout my application, at some point I am trying to get the last item that was added that meets the value of the two properties. For example, for all records where ID = 1 and Value = 2, there may be several. I need the last record.
I have been trying to use LINQ groupbys, the MyDataTable variable is my datatable.:
var groupQuery = from table in MyDataTable.AsEnumerable()
group table by new {column1 = table["PERSON_GU"], column2 = table["FIELD"]}
into groupedTable
select new
{
x = groupedTable.Key, // Each Key contains column1 and column2
y = groupedTable.Count()
};
I cant figure out how to make this select last though, it appears to return an anonymous type which is a little out of my development skill wheelhouse.
In summary, I have a datatable with two columns, I am trying to group my final datatable by these column values, and then get the last item.
If you want the last DataRow of each group:
var groupQuery =
from table in MyDataTable.AsEnumerable()
group table by new {column1 = table["PERSON_GU"], column2 = table["FIELD"]}
into groupedTable
select groupedTable.Last();
How to get a column value from a data table object. I have the id column on which basis I am trying to get another column value.
e.g. ApplicationId is the primary key column which I have and now I want to get the xyz column value for this ApplicationId.
I have accomplished my result by making use of the following Linq statement
List<string> lstResult= (from table in dt.AsEnumerable()
where table.Field<int>("Id") == id
select table.Field<string>("status")).ToList();
string dtStatus = lstResult[0];
you can do it lik this
var results = (from rows in dt.AsEnumerable() select new {resultcolumnname=row["resultcolumnname"]}).where(item=>item.columnname == value).ToList()
var x= from myrow in myDataTable.asEnumerable() where myrow.ApplicationId==[YourValue] select myRow.[ColumnYouWant];
I am not great when it comes to linq but this should do the trick.
I have the following scenario:
Table A that has 50 records and Table B that has 2 records.
I need to define a new table, say TableDiff which should contain 48 records from Table A that doesn't exist in Table B
My problem is that Table A and Table B are not identical but I have the field rowId which exists in both tables that I need to compare using it.
One way using Enumerable.Except and Enumerable.Join:
var aIDs = TableA.AsEnumerable().Select(r => r.Field<int>("RowID"));
var bIDs = TableB.AsEnumerable().Select(r => r.Field<int>("RowID"));
var diff = aIDs.Except(bIDs);
DataTable tblDiff = (from r in TableA.AsEnumerable()
join dId in diff on r.Field<int>("RowID") equals dId
select r).CopyToDataTable();
Here's the linq-to-objects "left-join"-approach:
DataTable tblDiff = (from rA in TableA.AsEnumerable()
join rB in TableB.AsEnumerable()
on rA.Field<int>("RowID") equals rB.Field<int>("RowID") into joinedRows
from ab in joinedRows.DefaultIfEmpty()
where ab == null
select rA).CopyToDataTable();
using System.Data.DataSetExtensions
var tableAIds = tableA.AsEnumerable().Select(row => (int)row["rowId"]);
var tableBIds = tableB.AsEnumerable().Select(row => (int)row["rowId"]);
var resultantIds = tableAIds.Except(tableBIds);
now for creating datatable again
DataTable diff = from myRow in tableA.AsEnumerable()
join rIDS resultantIds in myRow.Field<int>("rowId") equals rIDS
select myRow).CopyToDataTable()
I am using a Linq query to groupBy a column name and return a list of rows.
var query = from row in ProcessSummaryData.AsEnumerable()
group row by new { Key = row .Field<string>("GroupDescription") } into g
select new
{
GroupDescription = g.Key,
Values = g.ToList(),
};
The output of this query is something like this
GroupDescription Values
1 12,abc,xyz
12,abx,yut
13,tye,lki
2 14,asd,acd
Now the in the above example Values is a DataRow and I have just given an example of values in it.
Now what I want is that for GroupDescription '1' the output only has one row with '12' value.
I have tried a few things one of which is to have another Linq query on first list but that's over complicating things.
How do I use linq to group by first column and then use Distinct on certain column returned list to get only Distinct rows?
To get the first occurrence of a field's values you can group by that field and then take the first row of each grouping.
var query = from row in ProcessSummaryData.AsEnumerable()
group row by new { Key = row .Field<string>("GroupDescription") } into g
select new
{
GroupDescription = g.Key,
Values = (from value in g.ToList()
group value by value["Id"] into valueGroup
select valueGroup.First()).ToList()
};
I am using Linq to dataset to query a datatable. If i want to perform a group by on "Column1" on data table, I use following query
var groupQuery = from table in MyTable.AsEnumerable()
group table by table["Column1"] into groupedTable
select new
{
x = groupedTable.Key,
y = groupedTable.Count()
}
Now I want to perform group by on two columns "Coulmn1" and "Column2". Can anybody tell me the syntax or provide me a link explaining multiple group by on a data table??
Thanks
You should create an anonymous type to do a group by multiple columns:
var groupQuery = from table in MyTable.AsEnumerable()
group table by new { column1 = table["Column1"], column2 = table["Column2"] }
into groupedTable
select new
{
x = groupedTable.Key, // Each Key contains column1 and column2
y = groupedTable.Count()
}