Optimize Intellisense performance

src/OmniSharp.Roslyn.CSharp/Services/Intellisense/CompletionItemExtensions.cs

@@ -60,9 +60,13 @@ public static async Task<IEnumerable<ISymbol>> GetCompletionSymbolsAsync(this Co
             }
 
             // if the completion provider encoded symbols into Properties, we can return them
-            if (properties.ContainsKey(SymbolName) && properties.ContainsKey(SymbolKind))
+            if (properties.TryGetValue(SymbolName, out string symbolNameValue)
+                && properties.TryGetValue(SymbolKind, out string symbolKindValue)
+                && int.Parse(symbolKindValue) is int symbolKindInt)
             {
-                return recommendedSymbols.Where(x => x.Name == properties[SymbolName] && (int)x.Kind == int.Parse(properties[SymbolKind])).Distinct();
+                return recommendedSymbols
+                    .Where(x => (int)x.Kind == symbolKindInt && x.Name.Equals(symbolNameValue, StringComparison.OrdinalIgnoreCase))
+                    .Distinct();
             }
 
             return Enumerable.Empty<ISymbol>();

src/OmniSharp.Roslyn.CSharp/Services/Intellisense/IntellisenseService.cs

@@ -51,7 +51,7 @@ public async Task<IEnumerable<AutoCompleteResponse>> Handle(AutoCompleteRequest
 
                     // get recommended symbols to match them up later with SymbolCompletionProvider
                     var semanticModel = await document.GetSemanticModelAsync();
-                    var recommendedSymbols = await Recommender.GetRecommendedSymbolsAtPositionAsync(semanticModel, position, _workspace);
+                    var recommendedSymbols = (await Recommender.GetRecommendedSymbolsAtPositionAsync(semanticModel, position, _workspace)).ToArray();
 
                     var isSuggestionMode = completionList.SuggestionModeItem != null;
                     foreach (var item in completionList.Items)

src/OmniSharp.Roslyn/Extensions/StringExtensions.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 
 namespace OmniSharp.Extensions
@@ -16,12 +17,12 @@ public static bool IsValidCompletionStartsWithExactCase(this string completion,
 
         public static bool IsValidCompletionStartsWithIgnoreCase(this string completion, string partial)
         {
-            return completion.ToLower().StartsWith(partial.ToLower());
+            return completion.StartsWith(partial, StringComparison.OrdinalIgnoreCase);
         }
 
         public static bool IsCamelCaseMatch(this string completion, string partial)
         {
-            return new string(completion.Where(c => c >= 'A' && c <= 'Z').ToArray()).StartsWith(partial.ToUpper());
+            return new string(completion.Where(c => c >= 'A' && c <= 'Z').ToArray()).StartsWith(partial, StringComparison.OrdinalIgnoreCase);
         }
 
         public static bool IsSubsequenceMatch(this string completion, string partial)
@@ -31,7 +32,7 @@ public static bool IsSubsequenceMatch(this string completion, string partial)
                 return true;
             }
 
-            if (partial.Length > 1 && completion.ToLowerInvariant().Contains(partial.ToLowerInvariant()))
+            if (partial.Length > 1 && completion.IndexOf(partial, StringComparison.InvariantCultureIgnoreCase) >= 0)
             {
                 return true;
             }
@@ -54,7 +55,7 @@ private static bool FirstLetterMatches(string word, string match)
                 return false;
             }
 
-            return char.ToLowerInvariant(word.First()) == char.ToLowerInvariant(match.First());
+            return char.ToLowerInvariant(word[0]) == char.ToLowerInvariant(match[0]);
         }
     }
 }