IDataStore<TModel>.Sum(Func<TModel, long?> selector, Predicate<TModel> predicate) Method

.NET Standard 2.x

Computes the sum of a sequence of long? values that are obtained by invoking a transform function on each row of the primary buffer in DataStore.

Namespace: DWNet.Data

Assembly: DWNet.Data.dll

Syntax

long? Sum(Func<TModel, long?> selector, Predicate<TModel> predicate);

Parameters

selector Func<TModel, long?>

A transform function to apply to each row.

predicate System.Predicate<TModel>

A function to evaluate each row in the primary buffer for a condition.

Returns

Nullable<Long>

The sum of the sequence of values.

Examples

The following code example calculates the sum of those values (which are greater than 200000) in the budget column.

using Appeon.ApiDoc.Models;
using DWNet.Data;
using System;

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

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

        public void Example14()
        {
            // Instantiates a DataStore object with datawindow: d_department.
            var datastore = new DataStore<D_Department>(_context);

            // Retrieves rows from the database for datastore.
            datastore.Retrieve();

            Console.WriteLine("After Retrieve, Rowcount: {0}",
                              datastore.RowCount);

            // Calculates the sum of budget whose value is greater than 200000.
            long? sumvalue = datastore.Sum(m => (long?)m.Budget, m => m.Budget > 200000);

            Console.WriteLine("The sum of budget greater than 200000 is: {0}", sumvalue);

            /*This code produces the following output:
            
            After Retrieve, Rowcount: 4
            The sum of budget greater than 200000 is: 470000.0000
            */
        }
    }
}

Example Refer To

Model Class: D_Department
DataWindow File: d_department