DataGrid Self-Reference Hierarchy Dynamic Child Data Bind

I have used dynamic data binding in self reference heirarchy. i'm facing one issue while i'm expanding the row i have API call to load the chile data and for this i have used "LoadChildData" event. This event workinkg with static data but if i used API call it's not loaded child data in UI. API is working fine, it's return data also and i have assign it to grid but not able to see in UI. so can you please help me to fix this issue. I have attached My "LoadChildData" code and radzen grid code also.

async void LoadChildData(DataGridLoadChildDataEventArgs<IDictionary<string, object>> args)
{
string selectGroupIds = args.Item.Where(x => x.Key == "AccountGroupId").Select(x => x.Value).FirstOrDefault().ToString();
ViewModel Model = new ViewModel();

    Model.AccountGroups = selectGroupIds;
    Level1 = await ProjectsService.GetSubAccountGroupTotal(Model); 

    args.Data = Level1;
}

<RadzenDataGrid @ref="grid" AllowFiltering="false" AllowSorting="false" AllowColumnResize="true" ExpandMode="DataGridExpandMode.Single" Data="@dt" TItem="IDictionary<string, object>" LoadChildData="@LoadChildData" GridLines="@GridLines" RowCollapse="@(args => grid.ColumnsCollection.ToList().ForEach(c => c.ClearFilters()))" Style="width:1220px;" onscroll="scrollX">

@foreach (var column in columns)
{
<RadzenDataGridColumn TItem="IDictionary<string, object>" Title="@(@column.Key.Contains("d_") ? @ProjectsService.setDate(@column.Key) : "Group Name")" Type="column.Value" Property="@GetColumnPropertyExpression(column.Key, column.Value)" Width="180px">

@context[@column.Key]


}