Getting @ref from the grid before call to OnStateInit

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Martin Herløv
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Martin Herløv asked on 13 Dec 2021, 03:35 PM | edited on 13 Dec 2021, 04:26 PM

Hi I have made a utility class for helping with state management


<TelerikButton OnClick="@_gridStateManager.SaveState" Icon="download">Save State</TelerikButton>
<TelerikButton OnClick="@_gridStateManager.LoadState" Icon="upload">Load State</TelerikButton>
<TelerikButton OnClick="@_gridStateManager.ResetState" Icon="reset">Reset State</TelerikButton>

In the code behind file


 protected override async Task OnInitializedAsync()
{
     _gridStateManager = new GridStateManager<PortfolioListItem>(LocalStorage, PortfolioListGrid, GetDefaultGridState);
}

The problem is that the GridStateManger gets a null reference to the grid.

I know that the @ref is only safe to get in OnAfterRender / Async. How can I initialize the GridStateManager with the @ref set and also make it possible for the grid to call :


OnStateInit="@((GridStateEventArgs<PortfolioListItem> args) => _gridStateManager.OnStateInitHandler(args))">

In a safe way?

This is the code for my GridStateManager


using System;
using System.Threading.Tasks;
using Blazored.LocalStorage;
using Telerik.Blazor.Components;

namespace Argus.Client;

public class GridStateManager<T> where T : class
{
    private readonly ILocalStorageService _localStorage;
    private readonly TelerikGrid<T> _grid;
    private readonly Func<GridState<T>> _getDefaultGridState;
    private readonly string _stateStorageKey;

    public GridStateManager(
        ILocalStorageService localStorage,
        TelerikGrid<T> grid,
        Func<GridState<T>> getDefaultGridState)
    {
        _localStorage = localStorage;
        _grid = grid;
        _getDefaultGridState = getDefaultGridState;
        _stateStorageKey = $"GridStateFor{nameof(T)}";
    }

    public async Task OnStateInitHandler(GridStateEventArgs<T> args)
    {
        try
        {
            var storageState = await _localStorage.GetItemAsync<GridState<T>>(_stateStorageKey);
            if (storageState != null)
                args.GridState = storageState;
            if (storageState == null && _getDefaultGridState != null)
                args.GridState = _getDefaultGridState();
        }
        catch (Exception e)
        {
            Console.WriteLine(e);
        }
    }

    public async Task SaveState()
    {
        var gridState = _grid.GetState();
        await _localStorage.SetItemAsync(_stateStorageKey, gridState);
    }

    public async Task LoadState()
    {
        GridState<T> storedState = await _localStorage.GetItemAsync<GridState<T>>(_stateStorageKey);
        if (storedState != null)
        {
            await _grid.SetState(storedState);
        }
    }

    public async void ResetState()
    {
        if (_getDefaultGridState != null)
        {
            await _grid.SetState(_getDefaultGridState());
        }
        await _localStorage.RemoveItemAsync(_stateStorageKey);
    }
}


If I could get the grid reference in the OnStateInit  EventCallBack then I would have solved the problem

OnStateInit="@((GridStateEventArgs<PortfolioListItem> args) => _gridStateManager.OnStateInitHandler(args, @gridRef))">

 

I then tried to create the GridStateManger in the OnStateInit call from the grid. But I still don't have a valid ref to the grid, why?


OnStateInit="@((GridStateEventArgs<PortfolioListItem> args) => InitGridStateManager(args))">


private async Task InitGridStateManager(GridStateEventArgs<PortfolioListItem> args)
{
       _gridStateManager = new GridStateManager<PortfolioListItem>(LocalStorage, PortfolioListGrid, GetDefaultGridState);
       await _gridStateManager.OnStateInitHandler(args);
 }

 

Martin Herløv
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commented on 13 Dec 2021, 04:49 PM

Ended up wit setting the ref to the grid in OnAfterRender. Not so clean, but it works

protected override void OnAfterRender(bool firstRender)
        {
            if(firstRender)
            {
                _gridStateManager.Grid = PortfolioListGrid;
            }
        }

Marin Bratanov
Telerik team
commented on 14 Dec 2021, 05:50 AM

I think that's the only way to do this in Blazor, and the fact that you can't have a @ref sooner is one of the reasons why we made dedicated events for the grid state with suitable arguments.

Something else you could consider (but I have not tested and I don't know if it will work) is to use the setter of the field you point the @ref to to populate the service with that reference as well.

No answers yet. Maybe you can help?

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