How do I assign a string value to ienumerable<string> datatype?

Hi,

I have a RadzenDropDown component and it's bind-Value should be set 'Zero' on page load.

<RadzenDropDown AllowClear="true" AllowFiltering="true" FilterCaseSensitivity="FilterCaseSensitivity.CaseInsensitive"
                        @bind-Value=@productValue Multiple="true" Placeholder="Select" Data=@listProduct TextProperty="Name" ValueProperty="Code"/>
List<Product> listProduct = new List<Product>();
 IEnumerable<string> productValue = new string[] { };
 protected override async Task OnInitializedAsync()
    {
listProduct.Add(new Product{ Code = "0", Name = "All" });
listProduct.Add(new Product{ Code = "1", Name = "Product1" });
listProduct.Add(new Product{ Code = "2", Name = "Product2" });
listProduct.Add(new Product{ Code = "3", Name = "Product3" });
productValue  = ("0").Split(new string[] { "," }, StringSplitOptions.None);
}

How can I write productValue = "0" instead of productValue = ("0").Split(new string[] { "," }, StringSplitOptions.None); ?

There is a demo showing exactly how to specify initial selection for multi-select DropDown:

I have tried SelectedItem="0" SelectedItemsText="All" But it is not working. How can I do this instead of this line of code productValue = ("0").Split(new string[] { "," }, StringSplitOptions.None);

Check the code of the demo.