Fix code analysis suggestions

- Use `TryGetValue()` and `Count`/`Length` to improve performance.
- Fix typo in test name.
- Sort usings.

Author: martincostello

src/Microsoft.OpenApi/Validations/ValidationRuleSet.cs

@@ -2,9 +2,9 @@
 // Licensed under the MIT license.
 
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
-using System.Collections.Generic;
 
 namespace Microsoft.OpenApi
 {
@@ -150,12 +150,12 @@ public void Add(Type key, List<ValidationRule> rules)
         /// <exception cref="OpenApiException">Exception thrown when rule already exists.</exception>
         public void Add(Type key, ValidationRule rule)
         {
-            if (!_rulesDictionary.ContainsKey(key))
+            if (!_rulesDictionary.TryGetValue(key, out var rules))
             {
-                _rulesDictionary[key] = [];
+                _rulesDictionary[key] = rules = [];
             }
 
-            if (_rulesDictionary[key].Contains(rule))
+            if (rules.Contains(rule))
             {
                 throw new OpenApiException(SRResource.Validation_RuleAddTwice);
             }
@@ -202,7 +202,7 @@ public void Remove(string ruleName)
             }
 
             // Remove types with no rule
-            _rulesDictionary = _rulesDictionary.Where(r => r.Value.Any()).ToDictionary(r => r.Key, r => r.Value);
+            _rulesDictionary = _rulesDictionary.Where(r => r.Value.Count > 0).ToDictionary(r => r.Key, r => r.Value);
         }
 
         /// <summary>

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

@@ -59,7 +59,7 @@ public void RuleSetConstructorsReturnsTheCorrectRules()
         }
 
         [Fact]
-        public void RemoveValidatioRuleGivenTheValidationRuleWorks()
+        public void RemoveValidationRuleGivenTheValidationRuleWorks()
         {
             // Arrange
             var ruleSet = new ValidationRuleSet(_rulesDictionary);
@@ -162,7 +162,7 @@ public void TryGetValueWorks()
             ruleSet.TryGetValue(typeof(OpenApiContact), out var validationRules);
 
             // Assert
-            Assert.True(validationRules.Any());
+            Assert.True(validationRules.Count > 0);
             Assert.Contains(_contactValidationRule, validationRules);
         }
 
@@ -195,7 +195,7 @@ public void GetValidationRuleTypesReturnsAllSupportedTypes()
             var declaredRuleTypeProperties = typeof(ValidationRuleSet).Assembly.GetTypes()
                 .Where(t => t.IsClass
                             && t != typeof(object)
-                            && t.GetCustomAttributes(typeof(OpenApiRuleAttribute), false).Any())
+                            && t.GetCustomAttributes(typeof(OpenApiRuleAttribute), false).Length != 0)
                 .SelectMany(t2 => t2.GetProperties(BindingFlags.Static | BindingFlags.Public))
                 .ToList();