Inspectopedia 2025.2 Help

RoslynAnalyzers Do not call Enumerable.Cast<T> or Enumerable.OfType<T> with incompatible types

Enumerable.Cast and Enumerable.OfType require compatible types to function expectedly. The generic cast (IL 'unbox.any') used by the sequence returned by Enumerable.Cast will throw InvalidCastException at runtime on elements of the types specified. The generic type check (C# 'is' operator/IL 'isinst') used by Enumerable.OfType will never succeed with elements of types specified, resulting in an empty sequence. Widening and user defined conversions are not supported with generic types.

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

CA2021
Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | C# | Roslyn Analyzers

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection CA2021

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

Inspection Details

By default bundled with:

JetBrains Rider 2025.2, Qodana for .NET 2025.2,

Last modified: 18 September 2025