Cleaned up connection management code

src/Microsoft.SqlTools.ServiceLayer/Connection/Contracts/ConnectionSummaryComparer.cs

@@ -0,0 +1,53 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using System;
+using System.Collections.Generic;
+
+namespace Microsoft.SqlTools.ServiceLayer.Connection.Contracts
+{
+    
+    /// <summary>
+    /// Treats connections as the same if their server, db and usernames all match
+    /// </summary>
+    public class ConnectionSummaryComparer : IEqualityComparer<ConnectionSummary>
+    {
+        public bool Equals(ConnectionSummary x, ConnectionSummary y)
+        {
+            if(x == y) { return true; }
+            else if(x != null)
+            {
+                if(y == null) { return false; }
+
+                // Compare server, db, username. Note: server is case-insensitive in the driver
+                return string.Compare(x.ServerName, y.ServerName, StringComparison.OrdinalIgnoreCase) == 0
+                    && string.Compare(x.DatabaseName, y.DatabaseName, StringComparison.Ordinal) == 0
+                    && string.Compare(x.UserName, y.UserName, StringComparison.Ordinal) == 0;
+            }
+            return false;
+        }
+
+        public int GetHashCode(ConnectionSummary obj)
+        {
+            int hashcode = 31;
+            if(obj != null)
+            {
+                if(obj.ServerName != null)
+                {
+                    hashcode ^= obj.ServerName.GetHashCode();
+                }
+                if (obj.DatabaseName != null)
+                {
+                    hashcode ^= obj.DatabaseName.GetHashCode();
+                }
+                if (obj.UserName != null)
+                {
+                    hashcode ^= obj.UserName.GetHashCode();
+                }
+            }
+            return hashcode;
+        }
+    }
+}