Cannot access a disposed object in ASP.NET Core when injecting DbContext

Working with ASP.NET core I have seen this error multiple times and can be hard to debug. The error can have multiple root causes. It can be a real pain to find the cause and it is sometimes fixed by only taking care of the symptoms. By finding the root cause, you can take the appropriate action in your code.

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Add Index with Include Entity Framework Core

When creating indexes with code first migrations in Entity Framework Core you can create an index on a table by adding the following to your DbContext:

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);

    modelBuilder.Entity<table>() 
        .HasIndex(t =&gt; new { t.Column1, t.Column2}); }