add list of dynamic components in blazor

asp.net-core blazor c#

Question

I just started to have a look in blazor (v0.3) and doing some test I wanted to add a list using blazor

First I created a List<string> to test a simple list in the same page

<ul>
    @foreach (var item in listItems)
    {
        <li>@item</li>
    }
</ul>


@functions {

    private List<string> listItems = new List<string>();
    private string newItem;

    private void AddItem()
    {
        if (string.IsNullOrEmpty(newItem))
            return;

        listItems.Add(newItem);
        newItem = "";
    }

}

this is working fine, is adding every element to the list when I add it. but then, i tried to add components, add a single component was easy, based on this question here but for a list I had the next problem:

  • I created a <li> compontent just to test the functionality of components, here is the component view
<li id="@ID">
    @Text
</li>   




@functions {
  [Parameter]
  string Text { get; set; } 
  [Parameter]
  string ID { get; set; }
}
  • then in the parent view
<input type="text" bind="TxtExample" name="inpAdd"/>
  <button onclick="@addCompoment">add comp1</button>
<div class="simple-list-list">
    @if (!componentListTest.Any())
    {
        <p>You have no items in your list</p>
    }
    else
    {
        <ul>
            @foreach (var item in componentListTest)
            {
                @item
            }
        </ul>
    }
</div>

@functions {

    private List<RenderFragment> componentListTest { get; set; }
    private int currentCount {get; set;}
    private string TxtExample { get; set; }

    protected override void OnInit()
    {
        currentCount = 0;
        componentListTest = new List<RenderFragment>();
    }


    protected void addCompoment()
    {

        componentListTest.Add(CreateDynamicComponent(currentCount));
        currentCount++;
    }


    RenderFragment CreateDynamicComponent(int counter) => builder =>
    {
        var seq = 0;
        builder.OpenComponent(seq, typeof(listExample));
        builder.AddAttribute(++seq, "Text", "text --  "+TxtExample);
        builder.AddAttribute(++seq, "id","listed-"+counter);

        builder.CloseComponent();

    };
}

when I load the fist element is loaded correctly: enter image description here

but when I entered the second one, all of them are replaced for the last one:

enter image description here

Any idea whats going on?

1
1
5/11/2018 10:56:03 PM

Popular Answer

You are making it too complicated. You don't need to dynamically instantiate components for this scenario to work.

You can just do a:

<ul>
    @foreach (var item in listItems)
    {
        <myComponent bind-myVar="@item"></myComponent>
    }
</ul>

And the components will be instantiated for you.

Also see here how to make the parameters work on your component.

4
5/11/2018 9:04:15 PM


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