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CA2235: Mark all non-serializable fields

  • Article
Property Value
Rule ID CA2235
Title Mark all non-serializable fields
Category Usage
Fix is breaking or non-breaking Non-breaking
Enabled by default in .NET 9 No

Cause

An instance field of a type that is not serializable is declared in a type that is serializable.

Rule description

A serializable type is one that is marked with the System.SerializableAttribute attribute. When the type is serialized, a System.Runtime.Serialization.SerializationException exception is thrown if the type contains an instance field of a type that's not serializable and doesn't implement the System.Runtime.Serialization.ISerializable interface.

Tip

CA2235 does not fire for instance fields of types that implement ISerializable because they provide their own serialization logic.

How to fix violations

To fix a violation of this rule, apply the System.NonSerializedAttribute attribute to the field that is not serializable.

When to suppress warnings

Only suppress a warning from this rule if a System.Runtime.Serialization.ISerializationSurrogate type is declared that allows instances of the field to be serialized and deserialized.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

#pragma warning disable CA2235
// The code that's violating the rule is on this line.
#pragma warning restore CA2235

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

[*.{cs,vb}]
dotnet_diagnostic.CA2235.severity = none

For more information, see How to suppress code analysis warnings.

Example

The following example shows two types: one that violates the rule and one that satisfies the rule.

public class Mouse
{
    int buttons;
    string scanTypeValue;

    public int NumberOfButtons
    {
        get { return buttons; }
    }

    public string ScanType
    {
        get { return scanTypeValue; }
    }

    public Mouse(int numberOfButtons, string scanType)
    {
        buttons = numberOfButtons;
        scanTypeValue = scanType;
    }
}

[Serializable]
public class InputDevices1
{
    // Violates MarkAllNonSerializableFields.
    Mouse opticalMouse;

    public InputDevices1()
    {
        opticalMouse = new Mouse(5, "optical");
    }
}

[Serializable]
public class InputDevices2
{
    // Satisfies MarkAllNonSerializableFields.
    [NonSerialized]
    Mouse opticalMouse;

    public InputDevices2()
    {
        opticalMouse = new Mouse(5, "optical");
    }
}

Imports System
Imports System.Runtime.Serialization

Namespace ca2235

    Public Class Mouse

        ReadOnly Property NumberOfButtons As Integer

        ReadOnly Property ScanType As String

        Sub New(numberOfButtons As Integer, scanType As String)
            Me.NumberOfButtons = numberOfButtons
            Me.ScanType = scanType
        End Sub

    End Class

    <SerializableAttribute>
    Public Class InputDevices1

        ' Violates MarkAllNonSerializableFields.
        Dim opticalMouse As Mouse

        Sub New()
            opticalMouse = New Mouse(5, "optical")
        End Sub

    End Class

    <SerializableAttribute>
    Public Class InputDevices2

        ' Satisfies MarkAllNonSerializableFields.
        <NonSerializedAttribute>
        Dim opticalMouse As Mouse

        Sub New()
            opticalMouse = New Mouse(5, "optical")
        End Sub

    End Class

End Namespace

Remarks

Rule CA2235 does not analyze types that implement the ISerializable interface (unless they are also marked with the SerializableAttribute attribute). This is because rule CA2237 already recommends marking types that implement the ISerializable interface with the SerializableAttribute attribute.