Blazor value pass to the parent from dynamically rendered child

Question

I'm using Radzen data grid on my .NET core 3.1 blazor app. On the grid page I have RadzenDataGridColumn component and within that I have FilterTemplate component which is rendered dynamically. My problem is I want to bind FilterValue to the FilterTemplate component and the changes were made to the FilterValue should pass back to the parent level.

<RadzenDataGridColumn Property="@colDef.Property" FilterValue="@colDef.FilterValue" >                                              
    <FilterTemplate>
        <CascadingValue Value="@colDef.FilterValue">
            @colDef.FilterTemplate  //this contains a RenderFragment 
        </CascadingValue>   
    </FilterTemplate>                
</RadzenDataGridColumn>  

colDef.FilterTemplate can contain code snippet like bellow.

<RadzenDropDown TValue="string" @bind-Value="FilterValue" Data="@DrpData" TextProperty="@DrpTextProperty" ValueProperty="@DrpValueProperty" ></RadzenDropDown>  

@code {
    [CascadingParameter]
    public string FilterValue { get; set; }
    [Parameter]
    public string DrpTextProperty { get; set; }
    [Parameter]
    public string DrpValueProperty { get; set; }
    [Parameter]
    public IEnumerable<DrpDataType> DrpData { get; set; }
}

Answer 1

Use event callbacks, like in this example. I used the default Blazor wasm template and the existing Counter component to show how it works:

In child component (Counter.razor)

[Parameter]
public EventCallback<string> OnFilterValueChanged { get; set; }

private async Task IncrementCount()
{
    currentCount++;
    string newFilter = currentCount.ToString();
    await OnFilterValueChanged.InvokeAsync(newFilter);
}

The parent (Index.razor):

<Counter OnFilterValueChanged="FilterValueHandler" />
<h2>@FilterValue</h2>

@code {
public string FilterValue { get; set; } = "Initial Value";

private void FilterValueHandler(string filtervalue)
{
    FilterValue = filtervalue;
}
}

Now, when you click the button in child component, the variable value in parent component will get updated.