Question

I am trying to set a default value for a multi-valued parameter in Lightswitch but am having no luck.

For an example, I have a hardware inventory. “Hardware” table has fields of (‘active’, bool) and (‘company_id’,int).
Company_id is a foreign key to a Company table which contains a list of companies to select from.

I want to filter my Lightswitch screen based on these two field, but when the screen first loads I want it to default to the primary company, for active hardware.

I have created the Local Property for my ‘active’ parameter, added it to the screen.
Setting up the dropdown list for company parameter requires:

• Add Data Item (as a Query, selecting the table from my datasource, named Companies)
• Add Data Item (as Local Property of type Companies, named SelectedCompany)
• Binding query parameter to SelectedCompanies.company_id property
• Adding SelectedCompanies to the screen

I then specified the default values as such in code:

partial void Screen1_Created()
    {
        // Write your code here.
        SelectedCompanies.company_id = 2;
        selected_active_property = true;
    }

This works just fine for the ‘active’ parameter which is Boolean, however the SelectedCompanies line gives an intellisense error of:

Property or indexer “LightswitchApplication.company.company_id” cannot be assigned to — it is read only

Has anyone gotten a default value for this type of parameter working before?

Answer 1

In LightSwitch, you can’t set foreign keys directly. You have to retrieve the entity from the table, & assign that entity to the entity property.

So, in your case it would be:

partial void Screen1_Created()
{
    SelectedCompany = this.DataWorkspace.ApplicationData.Companies_SingleOrDefault(2);
    selected_active_property = true;
}