Created a helper class to use indexer and return search results

src/modules/launcher/Plugins/Wox.Plugin.Indexer/SearchHelper/WindowsSearchAPI.cs

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+using System;
+using System.Collections.Generic;
+using System.Data.OleDb;
+using Microsoft.Search.Interop;
+
+namespace Wox.Plugin.Indexer.SearchHelper
+{
+    public class WindowsSearchAPI
+    {
+        public IEnumerable<SearchResult> Search(string keyword, string pattern = "*", int offset = 0, int maxCount = 100)
+        {
+            // This uses the Microsoft.Search.Interop assembly
+            CSearchManager manager = new CSearchManager();
+
+            // SystemIndex catalog is the default catalog in Windows
+            ISearchCatalogManager catalogManager = manager.GetCatalog("SystemIndex");
+
+            // Get the ISearchQueryHelper which will help us to translate AQS --> SQL necessary to query the indexer
+            ISearchQueryHelper queryHelper = catalogManager.GetQueryHelper();
+
+            // Set the number of results we want. Don't set this property if all results are needed.
+            queryHelper.QueryMaxResults = maxCount;
+
+            // Set list of columns we want to display, getting the path presently
+            queryHelper.QuerySelectColumns = "System.ItemPathDisplay";
+
+            // Set additional query restriction
+            queryHelper.QueryWhereRestrictions = "AND scope='file:'";
+
+            // convert file pattern if it is not '*'. Don't create restriction for '*' as it includes all files.
+            if (pattern != "*")
+            {
+                pattern = pattern.Replace("*", "%");
+                pattern = pattern.Replace("?", "_");
+
+                if (pattern.Contains("%") || pattern.Contains("_"))
+                {
+                    queryHelper.QueryWhereRestrictions += " AND System.FileName LIKE '" + pattern + "' ";
+                }
+                else
+                {
+                    // if there are no wildcards we can use a contains which is much faster as it uses the index
+                    queryHelper.QueryWhereRestrictions += " AND Contains(System.FileName, '" + pattern + "') ";
+                }
+            }
+
+            // Set sorting order 
+            queryHelper.QuerySorting = "System.DateModified DESC";
+
+            // Generate SQL from our parameters, converting the userQuery from AQS->WHERE clause
+            string sqlQuery = queryHelper.GenerateSQLFromUserQuery(keyword);
+
+            // --- Perform the query ---
+            // create an OleDbConnection object which connects to the indexer provider with the windows application
+            using (System.Data.OleDb.OleDbConnection conn = new OleDbConnection(queryHelper.ConnectionString))
+            {
+                // open the connection
+                conn.Open();
+
+                // now create an OleDB command object with the query we built above and the connection we just opened.
+                using (OleDbCommand command = new OleDbCommand(sqlQuery, conn))
+                {
+                    // execute the command, which returns the results as an OleDbDataReader.
+                    using (OleDbDataReader WDSResults = command.ExecuteReader())
+                    {
+                        while (WDSResults.Read())
+                        {
+                            // col 0 is our path in display format
+                            Console.WriteLine("{0}", WDSResults.GetString(0));
+                            var result = new SearchResult { Path = WDSResults.GetString(0) };
+
+                            yield return result;
+                        }
+                    }
+
+                }
+            }
+
+        }
+    }
+}