The following code successfully renders the pdf viewer when the edit form is commented out, but when indside the pdf viewer it fails to render and gives the following error:
"Telerik.Blazor.Components.TelerikComboBox`2[Telerik.Blazor.Components.PdfViewer.Models.PdfViewerZoomLevelDescriptor,System.String] requires a value for the 'ValueExpression' ValueExpression is provided automatically when using 'bind-Value'.See more at https://docs.telerik.com/blazor-ui/knowledge-base/requires-valueexpression ."
 
 
@page "/pdfBug"

@* <EditForm Model="_fakeContext"> *@
    <TelerikPdfViewer Data="@PdfSource"
                      OnDownload="@OnPdfDownload"
                      Height="600px"></TelerikPdfViewer>
@* </EditForm> *@

@code {
    private byte[] PdfSource { get; set; }

    private async Task OnPdfDownload(PdfViewerDownloadEventArgs args)
    {
        args.FileName = "PDF-Viewer-Download";
    }

    protected override void OnInitialized()
    {
        PdfSource = Convert.FromBase64String(PdfBase64);

        base.OnInitialized();
    }

        private const string PdfBase64 = "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";
    private FakeContext _fakeContext = new FakeContext() { Name = "Test" };
    public class FakeContext
    {
        public string Name { get; set; }
    }
}
    

@using Telerik.DataSource
@using Telerik.DataSource.Extensions

Scroll through the groups or expand them to load their data on demand

<TelerikGrid TItem="@object"
             LoadGroupsOnDemand="true"
             Groupable="true"
             OnStateInit="@((GridStateEventArgs<object> args) => OnStateInitHandler(args))"
             OnRead="@ReadItems"
             ScrollMode="@GridScrollMode.Virtual" PageSize="20" RowHeight="60"
             Navigable="true" Sortable="true" FilterMode="@GridFilterMode.FilterRow" Height="600px">
    <GridColumns>
        <GridColumn Field="@nameof(Employee.Name)" FieldType="@typeof(string)" Groupable="false" />
        <GridColumn Field="@nameof(Employee.Team)" FieldType="@typeof(string)" Title="Team" />
        <GridColumn Field="@nameof(Employee.Salary)" FieldType="@typeof(decimal)" Groupable="false" />
        <GridColumn Field="@nameof(Employee.IsOnLeave)" FieldType="@typeof(bool)" Title="On Vacation" />
    </GridColumns>
</TelerikGrid>

@code {
    List<object> GridData { get; set; }

    protected async Task ReadItems(GridReadEventArgs args)
    {
        // sample data retrieval, see comments in the service mimic class below
        DataEnvelope<Employee> result = await MyService.GetData(args.Request);

        if (args.Request.Groups.Count > 0)
        {
            args.Data = result.GroupedData.Cast<object>().ToList();
        }
        else
        {
            args.Data = result.CurrentPageData.Cast<object>().ToList();
        }

        args.Total = result.TotalItemCount;
    }

    void OnStateInitHandler(GridStateEventArgs<object> args)
    {
        // set initial grouping
        GridState<object> desiredState = new GridState<object>()
        {
            GroupDescriptors = new List<GroupDescriptor>()
            {
                new GroupDescriptor()
                {
                    Member = "Team",
                    MemberType = typeof(string)
                },
                new GroupDescriptor()
                {
                    Member = "IsOnLeave",
                    MemberType = typeof(bool)
                }
            }
        };

        args.GridState = desiredState;
    }

    public class Employee
    {
        public int EmployeeId { get; set; }
        public string Name { get; set; }
        public string? Team { get; set; }
        public bool IsOnLeave { get; set; }
        public decimal Salary { get; set; }
    }

    public class DataEnvelope<T>
    {
        public List<AggregateFunctionsGroup> GroupedData { get; set; }
        public List<T> CurrentPageData { get; set; }
        public int TotalItemCount { get; set; }
    }

    public static class MyService
    {
        private static List<Employee> SourceData { get; set; }
        public static async Task<DataEnvelope<Employee>> GetData(DataSourceRequest request)
        {
            if (SourceData == null)
            {
                SourceData = new List<Employee>();
                var rand = new Random();
                for (int i = 1; i <= 3; i++)
                {
                    SourceData.Add(new Employee()
                    {
                        EmployeeId = i,
                        Name = "Employee " + i.ToString(),
                        Team = "Team " + i % 100,
                        IsOnLeave = i % 3 == 0,
                        Salary = rand.Next(1000, 5000)
                    });
                }
                SourceData.Add(new Employee()
                    {
                        EmployeeId = 3,
                        Name = "Employee " + 3.ToString(),
                        Team = null,
                        IsOnLeave = 3 % 3 == 0,
                        Salary = rand.Next(1000, 5000)
                    });
            }

            await Task.Delay(500);// deliberate delay to showcase async operations, remove in a real app

            // retrieve data as needed, you can find more examples and runnable projects here
            // https://github.com/telerik/blazor-ui/tree/master/grid/datasourcerequest-on-server
            var datasourceResult = SourceData.ToDataSourceResult(request);

            DataEnvelope<Employee> dataToReturn;

            if (request.Groups.Count > 0)
            {
                dataToReturn = new DataEnvelope<Employee>
                {
                    GroupedData = datasourceResult.Data.Cast<AggregateFunctionsGroup>().ToList(),
                    TotalItemCount = datasourceResult.Total
                };
            }
            else
            {
                dataToReturn = new DataEnvelope<Employee>
                {
                    CurrentPageData = datasourceResult.Data.Cast<Employee>().ToList(),
                    TotalItemCount = datasourceResult.Total
                };
            }

            return await Task.FromResult(dataToReturn);
        }
    }
}

An error occurred while starting the application.
DirectoryNotFoundException: C:\Users\VssAdministrator\.nuget\packages\telerik.ui.for.blazor.trial\1.2.0\staticwebassets\

Microsoft.Extensions.FileProviders.PhysicalFileProvider..ctor(string root, ExclusionFilters filters)

    DirectoryNotFoundException: C:\Users\VssAdministrator\.nuget\packages\telerik.ui.for.blazor.trial\1.2.0\staticwebassets\
        Microsoft.Extensions.FileProviders.PhysicalFileProvider..ctor(string root, ExclusionFilters filters)
        Microsoft.Extensions.FileProviders.PhysicalFileProvider..ctor(string root)
        Microsoft.AspNetCore.StaticWebAssetsFileProvider..ctor(string pathPrefix, string contentRoot)
        Microsoft.AspNetCore.StaticWebAssetsLoader+<>c.<UseStaticWebAssetsCore>b__2_0(ContentRootMapping cr)
        System.Linq.Enumerable+SelectEnumerableIterator<TSource, TResult>.MoveNext()
        System.Linq.Enumerable.OfTypeIterator<TResult>(IEnumerable source)+MoveNext()
        System.Collections.Generic.List<T>..ctor(IEnumerable<T> collection)
        System.Linq.Enumerable.ToList<TSource>(IEnumerable<TSource> source)
        Microsoft.AspNetCore.StaticWebAssetsLoader.UseStaticWebAssetsCore(IWebHostEnvironment environment, Stream manifest)
        Microsoft.AspNetCore.StaticWebAssetsLoader.UseStaticWebAssets(IWebHostEnvironment environment)
        Microsoft.AspNetCore.WebHost+<>c.<ConfigureWebDefaults>b__9_0(WebHostBuilderContext ctx, IConfigurationBuilder cb)
        Microsoft.AspNetCore.Hosting.Internal.GenericWebHostBuilder+<>c__DisplayClass8_0.<ConfigureAppConfiguration>b__0(HostBuilderContext context, IConfigurationBuilder builder)
        Microsoft.Extensions.Hosting.HostBuilder.BuildAppConfiguration()
        Microsoft.Extensions.Hosting.HostBuilder.Build()
        *.Program.Main(string[] args) in Program.cs

    System.IO.DirectoryNotFoundException: C:\Users\VssAdministrator\.nuget\packages\telerik.ui.for.blazor.trial\1.2.0\staticwebassets\

       at Microsoft.Extensions.FileProviders.PhysicalFileProvider..ctor(String root, ExclusionFilters filters)

       at Microsoft.Extensions.FileProviders.PhysicalFileProvider..ctor(String root)

       at Microsoft.AspNetCore.StaticWebAssetsFileProvider..ctor(String pathPrefix, String contentRoot)

       at Microsoft.AspNetCore.StaticWebAssetsLoader.<>c.<UseStaticWebAssetsCore>b__2_0(ContentRootMapping cr)

       at System.Linq.Enumerable.SelectEnumerableIterator`2.MoveNext()

       at System.Linq.Enumerable.OfTypeIterator[TResult](IEnumerable source)+MoveNext()

       at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)

       at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)

       at Microsoft.AspNetCore.StaticWebAssetsLoader.UseStaticWebAssetsCore(IWebHostEnvironment environment, Stream manifest)

       at Microsoft.AspNetCore.StaticWebAssetsLoader.UseStaticWebAssets(IWebHostEnvironment environment)

       at Microsoft.AspNetCore.WebHost.<>c.<ConfigureWebDefaults>b__9_0(WebHostBuilderContext ctx, IConfigurationBuilder cb)

       at Microsoft.AspNetCore.Hosting.Internal.GenericWebHostBuilder.<>c__DisplayClass8_0.<ConfigureAppConfiguration>b__0(HostBuilderContext context, IConfigurationBuilder builder)

       at Microsoft.Extensions.Hosting.HostBuilder.BuildAppConfiguration()

       at Microsoft.Extensions.Hosting.HostBuilder.Build()

       at *.Program.Main(String[] args) in d:\a\1\s\*\Program.cs:line 11

.NET Core 3.0.0-preview6-27804-01 X86 v4.0.0.0    |   Microsoft.AspNetCore.Hosting version 3.0.0-preview6.19307.2    |    Microsoft Windows 10.0.14393    |   Need help? 

<GridCommandColumn>

    @{

         var item = context as TheItem;
         <GridCommandButton Command="Edit" Icon="edit" Enabled="@!item.ReadOnly">Edit</GridCommandButton>
     }

</GridCommandColumn>