IDataStoreBase.RetrieveByKeyAsync(params object[] arguments) Method

.NET Standard 2.x

Asynchronously retrieves rows from the database. You can specify a value for a property with the [Key] attribute to retrieve rows to the DataStore.

Namespace: DWNet.Data

Assembly: DWNet.Data.dll

Syntax

public Task<int> RetrieveByKeyAsync(params object[] parameters)

Pararmeters

parameters System.Object[]

The value for the property with the [Key] attribute.

Returns

Task<int>

Returns a task that represents the asynchronous operation.

Remarks

After rows are retrieved, the DataStore's filter is applied. Therefore, any retrieved rows that do not meet the filter criteria are immediately moved to the filter buffer and are not included in the return count.

Before you can retrieve rows for the DataStore, you must specify a DataContext object with the constructor of DataStore or SetDataContext method to establish a database connection.

Normally, when you call the RetrieveByKeyAsync method, any rows that are already in the DataStore are discarded and replaced with the retrieved rows. You can set DwRetrieveEventArgs.IsResetBuffer to false in the RetrieveStart event to prevent this. In this case, RetrieveByKeyAsync adds any retrieved rows to the ones that already exist in the buffers.

Examples

The following code example demonstrates how to retrieve rows by key asynchronously from the database for DataStore.

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

namespace Appeon.ApiDoc.IDataStoreBaseExamples
{
    public class RetrieveByKeyAsyncExample
    {
        private readonly SchoolContext _context;
        
        public RetrieveByKeyAsyncExample(SchoolContext dataContext)
        {
            // Sets the data context
            _context = dataContext;
        }

        public async Task<int> Example1() 
        {
            // Instantiates a DataStore object with datawindow: d_department.
            var datastore = new DataStore("d_department", _context);
            
            int result = 0;
            
            try 
            {
                // Retrieves rows by key (DepartmentId = 1).
                result = await datastore.RetrieveByKeyAsync(1);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            
            // Gets the first row of data from the DataStore.
            var department = datastore.GetModel<D_Department>(0);
            
            Console.WriteLine("Rowcount: {0}", datastore.RowCount);
            Console.WriteLine("DepartmentID: {0}; Name: {1}; Budget: {2}",
                  department.Departmentid, department.Name, department.Budget);
                  
            return result;
                  
            /*This code produces the following output:
             
                Rowcount: 1
                DepartmentID: 1; Name: Engineering; Budget: 350000.0000
            */
        }
    }
}

Example Refer To

Model Class: D_Department
DataWindow File: d_department

Applies to

.NET Standard

2.x