SingleElementConcat

Diagnostic Rule Overview

Field	Value
ID	SHIMMER1101
Analyzer title	Simplify .Concat()
Analyzer message	Replace .Concat([e]) with .Append(e)
Code fix title	Replace .Concat([e]) with .Append(e)
Default severity	Info
Minimum framework/language version	N/A
Category	ShimmeringUsage
Link to code	SingleElementConcatAnalyzer.cs
Code fix exists?	Yes

Detailed Explanation

Using Enumerable.Concat() to add a single element is semantically imprecise and may mislead readers about the intent of the code. The analyzer flags these instances because .Concat() is designed for merging two enumerables, while .Append() more clearly indicates the addition of one element to an existing enumerable.

Examples

Flagged code:

var result = new[] { 1, 2 }.Concat(new[] { 3 });

Fixed code:

var result = new[] { 1, 2 }.Append(3);

Another scenario involving a cast:

Flagged code:

this._field = new[] { 1, 2 }.Concat((int[])[3]);

Fixed code:

this._field = new[] { 1, 2 }.Append(3);

Justification of the Severity

While the fixed code is more concise and clear, this has negligible impact on performance and does not cause any bugs.

When to Suppress

Suppress this diagnostic when you want to use .Concat() consistently.