IDE0059Unnecessary code rules (expression-level preferences)

The value is unused

Description

This rule flags unnecessary value assignments. For example:

You can take one of the following actions to fix this violation:

If the expression on the right side of the assignment has no side effects, remove the expression or the entire assignment statement. This improves performance by avoiding unnecessary computation.

If the expression on the right side of the assignment has side effects, replace the left side of the assignment with a discard (C# only) or a local variable that's never used. Discards improve code clarity by explicitly showing the intent to discard an unused value.

Example

// csharp_style_unused_value_assignment_preference = discard_variable
int GetCount(Dictionary<string, int> wordCount, string searchWord)
{
    _ = wordCount.TryGetValue(searchWord, out var count);
    return count;
}

// csharp_style_unused_value_assignment_preference = unused_local_variable
int GetCount(Dictionary<string, int> wordCount, string searchWord)
{
    var unused = wordCount.TryGetValue(searchWord, out var count);
    return count;
}

Configurable options

Vote for the value each option should take in the generated .editorconfig.

csharp_style_unused_value_assignment_preference

default: discard_variable

visual_basic_style_unused_value_assignment_preference

default: unused_local_variable

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