How to tell Resharper that the IEnumerable method removes nulls?

How to tell Resharper that the IEnumerable method removes nulls?

If you have a custom IEnumerable extension method that removes null elements from a collection and you want to tell ReSharper that it removes null elements, you can use the ContractAnnotation attribute.

Here's an example of how to use the ContractAnnotation attribute to tell ReSharper that a custom IEnumerable extension method removes null elements:

using System.Collections.Generic; using System.Diagnostics.CodeAnalysis; using JetBrains.Annotations; public static class EnumerableExtensions { [NotNull, ItemCanBeNull] [ContractAnnotation("null => null; notnull => notnull")] public static IEnumerable<T> RemoveNulls<T>([CanBeNull] this IEnumerable<T> source) { return source?.Where(x => x != null); } }

In this example, the ContractAnnotation attribute is applied to the RemoveNulls method. The "null => null; notnull => notnull" expression specifies that if the input parameter is null, the method will return null, and if the input parameter is not null, the method will return a collection that is not null.

The NotNull and ItemCanBeNull attributes are also applied to the method to specify that the method returns a collection that is not null, but may contain null elements.

With this setup, ReSharper will understand that the RemoveNulls method removes null elements from a collection, and will no longer raise warnings about null elements in the returned collection.

Examples

  1. "Resharper IEnumerable null check"

    • Description: Explore how to instruct Resharper to handle null values when working with IEnumerable methods.
    // Example Code: var nonNullItems = collection.Where(item => item != null);

  2. "Resharper annotate IEnumerable nullability"

    • Description: Learn how to use Resharper annotations to specify the nullability of elements in an IEnumerable.
    // Example Code: [ItemNotNull] var nonNullItems = collection.Where(item => item != null);

  3. "Resharper code inspection IEnumerable null"

    • Description: Implement Resharper code inspections to identify and handle potential nulls in IEnumerable methods.
    // Example Code: // ReSharper disable PossibleMultipleEnumeration var nonNullItems = collection?.Where(item => item != null).ToList(); // ReSharper restore PossibleMultipleEnumeration

  4. "Resharper nullable reference types IEnumerable"

    • Description: Explore how to leverage nullable reference types in Resharper when working with IEnumerable.
    // Example Code: IEnumerable<string?> nullableStrings = GetNullableStrings();

  5. "Resharper suppress nullability warning IEnumerable"

    • Description: Suppress Resharper warnings related to nullability when using IEnumerable methods.
    // Example Code: #nullable disable warnings var processedItems = collection.Where(item => item != null); #nullable restore

  6. "Resharper handle null values LINQ methods"

    • Description: Learn techniques for handling null values in LINQ methods within Resharper.
    // Example Code: var nonNullItems = collection.Where(item => item != null).ToList();

  7. "Resharper nullable analysis IEnumerable"

    • Description: Understand how Resharper performs nullable analysis on IEnumerable methods and customize it.
    // Example Code: var nonNullItems = collection.Where(item => item != null).ToList()!;

  8. "Resharper suppress null check warning"

    • Description: Suppress Resharper warnings regarding null checks in IEnumerable methods.
    // Example Code: // ReSharper disable once ConditionIsAlwaysTrueOrFalse var filteredItems = collection.Where(item => item != null);

  9. "Resharper configure nullability IEnumerable"

    • Description: Configure Resharper settings to tailor the nullability handling for IEnumerable methods.
    // Example Code: // ReSharper disable AssignNullToNotNullAttribute var nonNullItems = collection.Where(item => item != null).ToList(); // ReSharper restore AssignNullToNotNullAttribute

  10. "Resharper nullable enable IEnumerable"

    • Description: Enable nullable reference types and explore its impact on IEnumerable methods in Resharper.
    // Example Code: #nullable enable var nonNullItems = collection.Where(item => item != null).ToList(); #nullable restore

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