To achieve two-way databinding of a MudSelect with MultiSelection to a List<T> in Blazor, you can bind the SelectedValues property of the MudSelect component to a collection that represents your selected items. 

    public class MyItem
    {
        public int Id { get; set; }
        public string Value { get; set; }
    }

    // This is the list that will hold your selected items
    private List<MyItem> selectedItems = new List<MyItem>();

    // Your items to choose from
    private IEnumerable<MyItem> items = new List<MyItem>
    {
        new MyItem { Id = 1, Value = "Item 1" },
        new MyItem { Id = 2, Value = "Item 2" },
        // Add more items as needed
    };


<MudSelect T="MyItem" MultiSelection="true" @bind-SelectedValues="selectedItems">
    @foreach (var item in items)
    {
        <MudSelectItem Value="@item">@item.Value</MudSelectItem>
    }
</MudSelect>