Introduction
Grouping
on data is common requirement in finance and data applications, programmers write
Frequently code to perform these operations. In old applications architects
prefer grouping logic in database programming only and they use front end coding
to display grouped data.
Now LINQ provides easier and
faster approach to query over data using LINQ to entities and LINQ to Data-set.
In this
article I will explains in detail,
a. How I can Group data using LINQ?
b. How I can group data with multiple columns
using lambda?
c. How I can group data with multiple columns
using linq but not using any extension method?
Group by in LINQ
Grouping is one of the most
powerful capabilities of LINQ. In this example I will explain grouping using
LINQ with following sample examples.
1. Groping List data with single property.
2. Grouping List data with multiple properties.
3. Grouping Data Table data with single columns.
4. Grouping
Data Table data with multiple columns.
5. Grouping Data with Bool Value
You can perform grouping using group
clause and GroupBy() extension method same I
performed with following examples.
group clause
The group clause returns a
sequence of IGrouping<TKey, TElement> objects that contain zero or more
items that match the key value for the group.
GroupBy() Method
Groups the elements of a sequence
according to a specified key selector function and projects the elements for
each group by using a specified function.
Groping List data with single property
Using group clause (Grouping by string)
The following example shows how
to group source elements by using a single property of the element as the group
key. In this case the key is a string “UserName”.
var GroupUserByNames =
from user in activeUsers
group
user by user.UserName;
Using Group by Method
The following example shows how
to use GroupBy() extension method to group results with single property. In
this case the single group property is the UserName.
List<User> CheckDuplicateUsers= activeUsers.GroupBy(U =>
U.UserName).Where(gr => gr.Count() >
1).SelectMany(dupRec => dupRec).ToList();
Grouping List data with multiple properties
Using group clause (Group data by numeric range)
In this example
we used expression to create numeric group keys that represent a percentile
range. Note the use of let as a convenient location to store a method call
result, so that you do not have to call the method two times in the group clause.
var GroupProductByProfit=from product in products
let profitPercentage=GetProductProfit (product)
group new { product.Name, product.Type } by profitPercentage
into ProfitPercentGroup orderby ProfitPercentGroup.Key
select ProfitPercentGroup;
Using Group by Extension Method
List<BasicProduct> CheckDuplicateProducts = activeProducts.GroupBy(u =>
new { productCode=u.ProductCode,Type=u.ProductType}
).Where(gr => gr.Count() >1).SelectMany(dupRec => dupRec).ToList();
Grouping Data Table data with single columns:
Using group clause
Following example explains how to
use group by clause to group data with single column value (key value).
var GroupUserByNames = from user in UsersTablle.AsEnumerable()
group user by Field<string>("UserName") into newGroup
orderby newGroup.Key
select newGroup;
Using Group by Extension Method
Following example explains how to
use GrouBy() method to group data with single column value (key value).
DataTable duplicatesUsers =UsersTablle.AsEnumerable().GroupBy(x
=> x.Field<string>("UserName"))
.Where(gr => gr.Count() >1).SelectMany(dupRec => dupRec).ToList().CopyToDataTable();
Grouping Data Table data with
multiple columns
Using group clause (Grouping by Composite Keys)
Use a
composite key when you want to group elements according to more than one key.
You create a composite key by using an anonymous type or a named type to hold
the key element.
In this
example grouping is performed with two composite keys name and address.
var GroupUserByNames =
from user in UserTable.AsEnumerable()
group
user by new
{
Name =
user.Field<string >("Name"),
Address =
user.Field< string >("Address")
} into newGroup
orderby
newGroup.Key
select newGroup;
Using Group by Extension Method
//LINQ query retrieves duplicate records from data table
on two columns and save result in another table
DataTable resultTable = Data.AsEnumerable()
.GroupBy(row => new
{
UserName = row.Field<string>("UserName"),
OrignalAuthor = row.Field<string>("OrignalAuthor")
}).Where(gr => gr.Count() > 1).SelectMany(dupRec =>
dupRec).ToList().CopyToDataTable();
Grouping Data by using Bool Value
Following
example group employees those eligible for taxable income and not eligible for
taxable income, Grouping is performed with bool values.
// Group by true or false.
Var GroupEmployeByPackage=
from employee in employees
group employee by employee.package >=500000;//taxable or nontaxable!
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