Complex LINQ or EF query - linq

Question

I have the following 3 classes.
A workflow configuration has one brand and one workflowtype.
I need one method in linq or EF that gets me all the brands of existing workflowconfiguration and another method that gets me all the brands of non existing workflow configuration.
I am lost cause I dont know where to start.
public class Brand
{
public int BrandId { get; set; }
public string Name { get; set; }
}
public class WorkflowType
{
public int WorkflowTypeId { get; set; }
public string Name { get; set; }
}
public class WorkflowConfiguration
{
public int WorkflowConfigurationId { get; set; }
public WorkflowType WorkflowType { get; set; }
public Brand Brand { get; set; }
public virtual ICollection<Approver> Approvers { get; set; }
}
Update1
Here are how my tables would look like and the expected result
Brand
Audi
Volkswagen
Mercedes
WorkflowTYpes
type 1
type 2
type 3
WorkflowConfiguration
brandid, workflowtype id
1 ------------ 1
1 -------------2
List<string> GetBrandsForExistingWorkflowType(string worfklowtype)
If I pass type1 to this method it should return:
Audi because for type1, audi exists on the table
List<string> GetBrandsForNonExistingWorkflowType(string workflowType)
If I pass type1 to this method it should return.
Volkswagen and Mercedes because for type1, those 2 brands are not in the relationship.

Answer 1

I think this is what you want:
List<string> GetBrandsForExistingWorkflowType(string worfklowtype)
{
var result = db.WorkflowConfigurations
.Where(x => x.WorkflowType.Name == worfklowtype)
.Select(x => x.Brand);
return result;
}
List<string> GetBrandsForNonExistingWorkflowType(string workflowType)
{
var excluded = GetBrandsForExistingWorkflowType(string worfklowtype);
var result = db.Brands.Except(excluded);
return result;
}