IDataStore<TModel>. GroupBy<TKey, TElement>(Func<TModel, TKey> keySelector, Func<TModel, TElement> elementSelector) Method

.NET Standard 2.x

Groups rows of the primary buffer by the level of grouping criteria of DataStore. The sort criteria can be specified.

Namespace: DWNet.Data

Assembly: DWNet.Data.dll

Syntax

IEnumerable<IGrouping<TKey, TElement>> GroupBy<TKey, TElement>(Func<TModel, TKey> keySelector, Func<TModel, TElement> elementSelector);

Type Parameters

TKey

TElement

Parameters

keySelector Func<TModel, TKey>

A Func<Object, TModel> used to define the grouping criteria.

elementSelector Func<TModel, TElement>

A transform function to apply to each row.

Returns

IEnumerable<IGrouping<TKey, TElement>>

Returns an IEnumerable<IGrouping<TKey,TElement>> object which can be used to read data in groups.

Examples

The 'd_department_course' contains two levels of groups: the primary group is grouped by course_departmentid; the nested group is grouped by course_courseid. The following code example demonstrates how to get the primary group and return the data for the specified element.

using Appeon.ApiDoc.Models;
using DWNet.Data;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Appeon.ApiDoc.IDataStore_GenericExamples
{
    public class GroupByExample
    {
        private readonly SchoolContext _context;

        public GroupByExample(SchoolContext dataContext)
        {
            // Sets the data context
            _context = dataContext;
        }

        public void Example3()
        {
            // Instantiates a DataStore object with datawindow: d_department_course.
            var datastore = new DataStore<D_Department_Course>(_context);

            datastore.Retrieve();

            // The primary group is by course_departmentid which has only 4 values.
            var departmentGroup = datastore.GroupBy(a =>
                a.Course_Departmentid,
                b => new { b.Course_Title });

            Console.WriteLine("Department Group Count: {0}", departmentGroup.Count());

            /*This code produces the following output:
             
            Department Group Count: 4
            */
        }
    }

    public class Groupby_Key
    {
        public int Course_Departmentid { get; set; }
    }

    public class Groupby_Comparer : IEqualityComparer<Groupby_Key>
    {
        public bool Equals(Groupby_Key x, Groupby_Key y)
        {
            return x.Course_Departmentid == y.Course_Departmentid;
        }

        public int GetHashCode(Groupby_Key obj)
        {
            return obj.Course_Departmentid.GetHashCode();
        }
    }
}

Example Refer To

Model Class: D_Department_Course
DataWindow File: d_department_course