IDataStore.GroupBy<TModel>(int level, string sortKey = null) Method

.NET Standard 2.x

Generic method. 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

  public IEnumerable<IGrouping<object, TModel>> GroupBy<TModel>(int level, string sortKey = null);

Type Parameters

TModel

The type of a model class that matches with the current DataObject.

Parameters

level System.Int32

The level of grouping criteria of DataStore.

It is the number of a group defined in the DataWindow object which starts from 1.

sortkey System.String

A string whose value is the valid sort criteria for the DataStore. The expression includes column names or numbers. A column number must be preceded by a pound sign (#).

Default is null which indicates it will use the current sort criteria in DataStore.

Returns

System.Collections.Generic.IEnumerable<IGrouping<System.Object, TModel>>

Returns an IEnumerable<IGrouping<Object,IGroupingGetter<TModel>>> object which can be used to read data in groups.

Examples

The d_department_course DataStore 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 and the nested groups and return the TModel data of these groups.

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

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

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

        public void Example4()
        {
            // 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<D_Department_Course>(1);

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

            // The nested group is by course_courseid which has only 9 values.
            var courseGroup = datastore.GroupBy<D_Department_Course>(2);

            Console.WriteLine("Course Group Count: {0}",
                courseGroup.Count());

            // Changes sort to sort by course_title; then get the primary group again.
            departmentGroup = datastore.GroupBy<D_Department_Course>(1, "course_title");

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

            /*This code produces the following output:
             
            Department Group Count: 4
            Course Group Count: 9
            SortBy course_title, Department Group Count: 7
            */
        }
    }
}

Example Refer To

Model Class: D_Department_Course
DataWindow File: d_department_course

Applies to

.NET Standard

2.x