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Tweak DbSet nullability docs #2577

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Aug 20, 2020
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Tweak DbSet nullability docs #2577

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4 changes: 3 additions & 1 deletion entity-framework/core/miscellaneous/nullable-reference-types.md
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Expand Up @@ -20,10 +20,12 @@ The main documentation on required and optional properties and their interaction

## DbContext and DbSet

When nullable reference types are enabled, the C# compiler emits warnings for any uninitialized non-nullable property, as these would contain null. As a result, the common practice of having uninitialized DbSet properties on a context type will now generate a warning. To fix this, make your DbSet properties read-only and initialize them as follows:
When nullable reference types are enabled, the C# compiler emits warnings for any uninitialized non-nullable property, as these would contain null. As a result, the common practice of having uninitialized DbSet properties on a context type will now generate a warning. This can be fixed as follows:

[!code-csharp[Main](../../../samples/core/Miscellaneous/NullableReferenceTypes/NullableReferenceTypesContext.cs?name=Context&highlight=3-4)]

Another strategy is to use non-nullable auto-properties, but to initialize them to null, using the null-forgiving operator (!) to silence the compiler warning. The DbContext constructor ensures that all DbSet properties will get initialized, and null will never be observed on them.

## Non-nullable properties and initialization

Compiler warnings for uninitialized non-nullable reference types are also a problem for regular properties on your entity types. In our example above, we avoided these warnings by using [constructor binding](xref:core/modeling/constructors), a feature which works perfectly with non-nullable properties, ensuring they are always initialized. However, in some scenarios constructor binding isn't an option: navigation properties, for example, cannot be initialized in this way.
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