Property not a single value

Hi,
I have been stuck with this problem for weeks now and I can't figure it out.
In my datagrid, I have a property "TestEtanchieteExternes" that is a collection because I'm calling a foreign table and I would like to manage my filter. However, it gives me this error :

error :

I believe the reason is that it's acting as if TestEtanchieteExterne is a single value when it's actually a collection.

How can I fix this ? I believe I need to point to the first item in my TestEtanchieteExterne collection in Property attribute but I don't know how to do that.

Please I really need your help.

You can remove Property setting from this column and use FilterTemplate to implement your own filtering.

Thank you. I don't have that error anymore. However, what am I supposed to do in the FilterTemplate ? In the picture you can see that I already use it. Should I call LoadData() in my OnSelectedOrificeChange() method and try to pass the Orifice's filter value to it ?

You can check our demos for reference. For example:

I don't see what I am looking for in the demos. Now that I removed Property attribute, the filter value on LoadDataArgs is empty.

Is this not your case here with multivalued filter? Blazor DataGrid custom filtering (radzen.com)

<RadzenDataGridColumn TItem="Employee" Title="Customer" Property="CompanyName" Type="typeof(IEnumerable<string>)" FilterValue="@selectedCompanyNames" FilterOperator="FilterOperator.Contains" LogicalFilterOperator="LogicalFilterOperator.Or">
    <FilterTemplate>
        <RadzenDropDown @bind-Value=@selectedCompanyNames Style="width:100%;" Change=@OnSelectedCompanyNamesChange Data="@(companyNames)" AllowClear="true" Multiple="true" />
    </FilterTemplate>
</RadzenDataGridColumn>