Update MongoDb

Src/Asp.NetCore2/SqlSugar.MongoDbCore/Extensions.cs

@@ -0,0 +1,21 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace SqlSugar.MongoDb
+{
+    public static class Extensions
+    {
+        public static bool EqualCase(this string thisValue, string equalValue)
+        {
+            if (thisValue != null && equalValue != null)
+            {
+                return thisValue.ToLower() == equalValue.ToLower();
+            }
+            else
+            {
+                return thisValue == equalValue;
+            }
+        }
+    }
+}