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

<DxTagBox Data="@Cities"
          AllowCustomTags="true"
          Tags="@Tags"
          TagsChanged="@TagsChanged"
          @bind-Values="@Values">
</DxTagBox>

@code {
    IEnumerable<string> Tags = new List<string>() {
        "London",
        "New York"
    };

    IEnumerable<string> Cities = new List<string>() {
        "London",
        "Berlin",
        "Paris",
    };

    IEnumerable<string> Values;

    void TagsChanged(IEnumerable<string> newTags) {
        Tags = newTags;
    }
}