Replaced ContainsKey and [] with TryGetValue (#1339)

Dapper.Contrib/SqlMapperExtensions.cs

@@ -541,9 +541,9 @@ private static ISqlAdapter GetFormatter(IDbConnection connection)
             var name = GetDatabaseType?.Invoke(connection).ToLower()
                        ?? connection.GetType().Name.ToLower();
 
-            return !AdapterDictionary.ContainsKey(name)
-                ? DefaultAdapter
-                : AdapterDictionary[name];
+            return AdapterDictionary.TryGetValue(name, out var adapter)
+                ? adapter
+                : DefaultAdapter;
         }
 
         private static class ProxyGenerator