Sample reproducible with workaround (to initialize the data source so it is not null) is below
Sample error and stack trace
ArgumentNullException: Value cannot be null. (Parameter 'source')
<TelerikGrid Data=@GridData Pageable="true" Height="300px">
<GridColumns>
<GridColumn Field="@(nameof(Employee.EmployeeId))">
<FooterTemplate>
some footer
</FooterTemplate>
</GridColumn>
<GridColumn Field=@nameof(Employee.Salary) Title="Salary">
</GridColumn>
<GridColumn Field=@nameof(Employee.Name)>
</GridColumn>
</GridColumns>
</TelerikGrid>
@code {
public List<Employee> GridData { get; set; } // = new List<Employee>(); // workaround
public class Employee
{
public int EmployeeId { get; set; }
public string Name { get; set; }
public decimal Salary { get; set; }
}
}