Use Linq Count() extension method to get the number of elements in collection

Author: MaggieKimani1

src/Microsoft.OpenApi.Readers/OpenApiYamlDocumentReader.cs

@@ -68,7 +68,7 @@ public OpenApiDocument Read(YamlDocument input, out OpenApiDiagnostic diagnostic
             }
 
             // Validate the document
-            if (_settings.RuleSet != null && _settings.RuleSet.Rules.Count > 0)
+            if (_settings.RuleSet != null && _settings.RuleSet.Rules.Count() > 0)
             {
                 var openApiErrors = document.Validate(_settings.RuleSet);
                 foreach (var item in openApiErrors.OfType<OpenApiValidatorError>())
@@ -112,7 +112,7 @@ public async Task<ReadResult> ReadAsync(YamlDocument input)
             }
 
             // Validate the document
-            if (_settings.RuleSet != null && _settings.RuleSet.Rules.Count > 0)
+            if (_settings.RuleSet != null && _settings.RuleSet.Rules.Count() > 0)
             {
                 var openApiErrors = document.Validate(_settings.RuleSet);
                 foreach (var item in openApiErrors.OfType<OpenApiValidatorError>())
@@ -193,7 +193,7 @@ public T ReadFragment<T>(YamlDocument input, OpenApiSpecVersion version, out Ope
             }
 
             // Validate the element
-            if (_settings.RuleSet != null && _settings.RuleSet.Rules.Count > 0)
+            if (_settings.RuleSet != null && _settings.RuleSet.Rules.Count() > 0)
             {
                 var errors = element.Validate(_settings.RuleSet);
                 foreach (var item in errors)

test/Microsoft.OpenApi.Tests/Validations/ValidationRuleSetTests.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
+using System.Linq;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -43,7 +44,7 @@ public void DefaultRuleSetPropertyReturnsTheCorrectRules()
             Assert.NotEmpty(rules);
 
             // Update the number if you add new default rule(s).
-            Assert.Equal(22, rules.Count);
+            Assert.Equal(22, rules.Count());
         }
     }
 }