IDataStoreBase.UpdateAsync(bool resetFlag, CancellationToken cancellationToken) Method

.NET Standard 2.x

Asynchronously updates the database with the changes made in the DataStore.

Namespace: DWNet.Data

Assembly: DWNet.Data.dll

Syntax

public Task<int> UpdateAsync(bool resetFlag, CancellationToken cancellationToken)

Parameters

resetflag System.Boolean

A Boolean value specifying whether DataStore should automatically reset the update flags:

True -- To reset the flags.

False -- Not to reset the flags.

cancellationToken CancellationToken

A cancellation token that can be used by other objects or threads to receive notice of cancellation.

Returns

Task<int>

Returns a task that represents the asynchronous operation.

Remarks

You must use the constructor of DataStore or SetDataContext method to specify the database connection before the UpdateAsync method is executed.

By default, UpdateAsync resets the update flags after successfully completing the update. However, you can prevent the flags from being reset until after you perform other validations and commit the changes. When you are satisfied with the update, call ResetUpdate to clear the flags so that items are no longer marked as modified.

If you call the UpdateAsync method with the resetflag argument set to false and do not call ResetUpdate, the DataStore will attempt to issue the same SQL statements again the next time you call UpdateAsync.

Test success/failure code

It is a good practice to test the success/failure code after calling the UpdateAsync method. You can also verify the number of rows inserted, updated, and deleted by a DataStore update by examining the values of the arguments of the UpdateEnd event.

Updating several tables in one DataStore

If you want to update several tables in one DataStore, you can use the Modify to change the Update property of columns in each table. To preserve the status flags of the rows and columns, set the resetflag argument to false. Because the updates all occur in the same DataStore, you cannot allow the flags to be cleared until all the tables have used them. When all the updates are successfully completed and committed, you can call ResetUpdate to clear the changed flags in the DataStore.

Updating multiple DataStores

If you are updating multiple DataStores as part of one transaction, set the resetflag argument to false. This will prevent the DataStore from "forgetting" which rows to update in case one of the updates fails. You can roll back, try to correct the situation, and update again. Once all of the DataStores have been updated successfully, use the DataContext.Commit method to finalize the transaction and use ResetUpdate to reset the DataStore's status flags.

Events

UpdateAsync can trigger UpdateStart and UpdateEnd events.

Examples

The following code example adds a data record to the end of the DataStore and then updates the change asynchronously to the database. It uses a CancellationTokenSource type parameter to make this operation cancelable.

using System;
using System.Threading;
using System.Threading.Tasks;
using DWNet.Data;
using SnapObjects.Data;

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

        public async Task<int> Example3(bool resetFlag, CancellationTokenSource cts) 
        {
            // Instantiates a DataStore object with datawindow: d_department.
            var datastore = new DataStore("d_department", _context);
            
            Console.WriteLine("Retrieved Rowcount: {0}", datastore.Retrieve());
            
            // Modifies the value for the budget column in the first row.
            datastore.SetItem(0, "budget", 330000.00m);
            
            // Adds a row to the end of DataStore.
            int row = datastore.AddRow();
            datastore.SetItem(row, "Departmentid", 10);
            datastore.SetItem(row, "Name", "New Department");
            datastore.SetItem(row, "Budget", 10000m);
            datastore.SetItem(row, "Startdate", DateTime.Now);
            datastore.SetItem(row, "Administrator", 2);
            
            int AffectedRow = 0;
            
            try
            {
                // Call asynchronous update to commit the changes to the database.
                // If a task has been cancelled, the call to the 
                // DataStore.UpdateAsync method throws an OperationCanceledException.
                AffectedRow = await datastore.UpdateAsync(resetFlag, cts.Token);
                
                Console.WriteLine("After Add, Update and Retrieve, Rowcount: {0}", AffectedRow);
            }
            catch (OperationCanceledException e)
            {
                // The operation was cancelled before completion.
                Console.WriteLine(e.Message);
            }
            catch (Exception e)
            {
                Console.WriteLine(e.Message);
            }
            finally
            {
                cts.Dispose();
            }
            
            return AffectedRow;
            
            /*This code produces the following output:
            
                A task was canceled.        
            */
        }
    }
}

Example Refer To

Model Class: D_Department
DataWindow File: d_department

Applies to

.NET Standard

2.x