Cannot access a @context.field in <SelectedTemplate> in Blazored Typeahead

I have a problem with Typeahead with my Blazor-Server app:

<BlazoredTypeahead style="width: auto" SearchMethod="SearchUser"
                                       @bind-Value="calc.FkCustomerId">
                        <SelectedTemplate>
                            @context.AccountCode
                        </SelectedTemplate>
                        <ResultTemplate>
                            @context.CustomerSname (@context.AccountCode)
                        </ResultTemplate>
                    </BlazoredTypeahead>
    @{    

              private async Task<IEnumerable<AutolineAccts>> SearchUser(string SelectedUser)
              {
                    return await Task.FromResult(alContext.AutolineAccts.Where(x => x.CustomerSname.Contains(SelectedUser)).ToList());
            }
}

The problem I have occurs in the SelectedTemplate part:

'string' does not contain a definition for 'AccountCode' and no accessible extension method 'AccountCode' accepting a first argument of type 'string' could be found

Intellisense is supposed to show me all the fields of AutolineAccts, but it does not. But it works for the @context object within the node

'string' does not contain a definition for 'AccountCode' and no accessible extension method 'AccountCode' accepting a first argument of type 'string' could be found

The conext in <SelectedTemplate> is corresponding to that in @bind-Value, seems that calc.FkCustomerId is a string type value, and it definetely doesn't have a AccountCode property, so the above error occurs.

You can refer to this article for how to use Blazored Typeahead.