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Use 'System.HashCode.Combine' (IDE0070)

  • Article
Property Value
Rule ID IDE0070
Title Use System.HashCode.Combine
Category Style
Subcategory Language rules (expression-level preferences)
Applicable languages C# and Visual Basic

Overview

This rule recommends the use of the System.HashCode.Combine method to compute a hash code instead of using custom hash code computation logic.

Options

This rule has no associated code-style options.

Example

class B
{
    public override int GetHashCode() => 0;
}

class C : B
{
    int j;

    // Code with violations
    public override int GetHashCode()
    {
        // IDE0070: GetHashCode can be simplified.
        var hashCode = 339610899;
        hashCode = hashCode * -1521134295 + base.GetHashCode();
        hashCode = hashCode * -1521134295 + j.GetHashCode();
        return hashCode;
    }

    // Fixed code
    public override int GetHashCode()
    {
        return System.HashCode.Combine(base.GetHashCode(), j);
    }
}

Suppress a warning

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

#pragma warning disable IDE0070
// The code that's violating the rule is on this line.
#pragma warning restore IDE0070

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

[*.{cs,vb}]
dotnet_diagnostic.IDE0070.severity = none

To disable all of the code-style rules, set the severity for the category Style to none in the configuration file.

[*.{cs,vb}]
dotnet_analyzer_diagnostic.category-Style.severity = none

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

See also