Entity Framework Multiple Column as Primary Key by Fluent Api
Use anonymous type object instead of 2 separated statements:
HasKey(pc => new { pc.ProductId, pc.CategoryId });
From Microsoft Docs: EntityTypeConfiguration.HasKey Method
If the primary key is made up of multiple properties then specify an anonymous type including the properties. For example, in C#
t => new { t.Id1, t.Id2 }and in Visual Basic .NetFunction(t) New With { t.Id1, t.Id2 }.