.net: Handle all ambiguous keywords properly (#435)

By using the first duplicate keyword:

```
.ToDictionary(item => item.Key, item => item.First());
```

GherkinDialect assumes that the AsteriskKeyword is the only duplicate
keyword. Which probably isn't true.

By using `Unknown` in case of ambiguity:

```
.ToDictionary(item => item.Key, items => items.Count() == 1 ? items.First() : StepKeywordType.Unknown);
```

that problems is avoided.

Author: mpkorstanje

CHANGELOG.md

@@ -8,6 +8,7 @@ This document is formatted according to the principles of [Keep A CHANGELOG](htt
 
 ## [Unreleased]
 ### Fixed
+- [.Net] Handle all ambiguous keywords properly ([#435](https://github.com/cucumber/gherkin/pull/435))
 - [Java] Optimize `GherkinLine.substringTrimmed` ([#444](https://github.com/cucumber/gherkin/pull/444))
 - [Java] Improve performance with a generated keyword matcher ([#445](https://github.com/cucumber/gherkin/pull/445))
 
@@ -29,7 +30,6 @@ This document is formatted according to the principles of [Keep A CHANGELOG](htt
 - [Go] Trim trailing tab characters from title and step lines ([#441](https://github.com/cucumber/gherkin/pull/441))
 - [Java] Use a more consistent definition of whitespace ([#442](https://github.com/cucumber/gherkin/pull/442))
 
-
 ## [33.0.0] - 2025-07-07
 ### Changed
 - [Elixir, Go, JavaScript, Java, Perl, Php, Ruby] Update dependency messages to v28 ([#420](https://github.com/cucumber/gherkin/pull/420))

dotnet/Gherkin/GherkinDialect.cs

@@ -38,14 +38,15 @@ public class GherkinDialect(
         .OrderByDescending(x => x.Length) // To avoid conflicts when some keywords are prefixes of others, try the longest keywords first.
         .ToArray();
 
-    public IDictionary<string, StepKeywordType> StepKeywordTypes { get; } = new[] { new { Keyword = AsteriskKeyword, Type = StepKeywordType.Unknown } }
-        .Concat(givenStepKeywords.Select(kw => new { Keyword = kw, Type = StepKeywordType.Context }))
+    public IDictionary<string, StepKeywordType> StepKeywordTypes { get; } = 
+                givenStepKeywords.Select(kw => new { Keyword = kw, Type = StepKeywordType.Context })
         .Concat(whenStepKeywords.Select(kw => new { Keyword = kw, Type = StepKeywordType.Action }))
         .Concat(thenStepKeywords.Select(kw => new { Keyword = kw, Type = StepKeywordType.Outcome }))
         .Concat(andStepKeywords.Select(kw => new { Keyword = kw, Type = StepKeywordType.Conjunction }))
         .Concat(butStepKeywords.Select(kw => new { Keyword = kw, Type = StepKeywordType.Conjunction }))
         .GroupBy(item => item.Keyword, item => item.Type)
-        .ToDictionary(item => item.Key, item => item.First());
+        // Fold keywords with ambiguous keyword types into unknown 
+        .ToDictionary(item => item.Key, items => items.Count() == 1 ? items.First() : StepKeywordType.Unknown);
 
     public StepKeywordType? GetStepKeywordType(string keyword)
         => StepKeywordTypes.TryGetValue(keyword, out var tokenType) ? tokenType : null;