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Blazor Component TwoWay Databinding


By : CAPN
Date : October 16 2020, 06:10 AM
Any of those help This is a two-way data binding between components. This behavior (or limitation) is by design. What you do, is the correct way to solve it, and I may venture to say, a best practice, at least according Steve Anderson, others may suggest different methods, such as a service class.
Some explanation of what is going on: When you apply a change to the parent component, the change event is triggered, the state of the component has changed, and the component should be re-rendered. To re-render the parent component, the StateHasChanged method is called by Blazor automatically. But when a state is changed on the child component, the parent component is ignorant of this, and we should notify it of this. Again, using event call backs for this is a good practice, to my mind...
code :
// Define a method in the parent component which will be called 
// from the child component when the user tap the button residing 
// in the child component. This method has a string parameter passed
// from the child component
public void GetValueFromChild(string value)
 {
        // Do somethig with value
  } 
// When the user click the button the method GetValueFromChild
// defined on the parent component is called

<button class="btn" onclick=@(() => OnAddValue("some string value"))>Add</button>

    @functions
{
    // Define an Action delegate property which stores a reference
    // to A.GetValueFromChild
    // Parameters
    [Parameter] Action<string> OnAddValue{ get; set; }
}
// Here (in the parent component) you place the child component and
// set its OnAddValue to the name of the method to be called
<B OnAddValue = "GetValueFromChild"></B> 


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How do I fix this? TwoWay databinding not working


By : Fabrini Murta
Date : March 29 2020, 07:55 AM
With these it helps Yes, that's the way I would go. You could also add a binding to the slider instead of the textbox and get by without the UpdateSourceTrigger...
code :
<Slider x:Name="slider"
        VerticalAlignment="Bottom"
        Height="32.8"
        Value="{Binding ElementName=txtie, Path=Text, Mode=TwoWay}" />

what is the difference between TwoWay databinding and ObservableCollection?


By : Casey Davis
Date : March 29 2020, 07:55 AM
Hope that helps The two "things" TwoWay databinding and ObservableCollection are different things which can collaborate, but are not directly linked. Databinding is a concept and ObservableCollection is an implementation of an interface (INotifyCollectionChanged) which is used in the implementation of the concept of databinding in the .NET framework. In itself, INotifyCollectionChanged is a small part of this implementation.
In fact you can use TwoWay databinding without ObservableCollections and ObservableCollections without databinding.

Error when Databinding with mode=twoway


By : user3672316
Date : March 29 2020, 07:55 AM
may help you . Two-way binding to an entire object (a string in this case) makes no sense to Silverlight so it is correct to throw an exception. Shame it is not a more useful error message :)
When there is no Path in the binding the ItemsControl can fetch a value using Object.ToString(), but where will it store the result back? It can't replace the string as that would require placing a new string object back in the collection. Two-way binding is done via reflection against a property of an object.

Blazor TwoWay Binding on custom Component


By : user3248717
Date : March 29 2020, 07:55 AM
may help you . Ok so for anyone stumbling upon this. I tried a bit more and found a solution. So to my custom input component AnimatedUserInput I added a EventCallback which I call everytime the value on the input is updated:
code :
@code {

    [Parameter]
    public string TbText
    {
        get => _tbText;
        set
        {
            if (_tbText == value) return;

            _tbText = value;
            TbTextChanged.InvokeAsync(value);
        }
    }

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

    [Parameter]
    public string Placeholder { get; set; }

    private string _tbText;
}
<div class="edit-user-form">
    <AnimatedUserInput @bind-TbText="@User.ShortId" Placeholder="MHTEE Id"/>
    <AnimatedUserInput @bind-TbText="@User.FirstName" Placeholder="First name" />
    <AnimatedUserInput @bind-TbText="@User.LastName" Placeholder="Last name" />
    <AnimatedUserInput @bind-TbText="@User.UserName" Placeholder="Username" />
    <AnimatedUserInput @bind-TbText="@User.StaffType" Placeholder="Staff type" />
    <AnimatedUserInput @bind-TbText="@User.Token" Placeholder="Token" />
    <button class="btn btn-secondary" @onclick="Hide" style="{display:inline-block;}">Back</button>
    <button class="btn btn-primary" @onclick="SaveUser" style="{display:inline-block;}">Save</button>
</div>

@code {
    [Parameter] public vUser User { get; set; }
}

Blazor databinding to a javascript web component with complex object from C#


By : user3685561
Date : March 29 2020, 07:55 AM
I wish did fix the issue. Great question. I noticed also some issues with binding a web component directly via Blazor data binding, especially with the connectedCallback of the web component which is a kwown issue.
But the great thing is:
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