Remove unused

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlTypes/SqlJson.cs

@@ -22,8 +22,6 @@ public class SqlJson : INullable
         /// </summary>
         private bool _isNull;         
 
-        private readonly JsonDocument? _jsonDocument;
-
         private readonly string? _jsonString;
 
         /// <summary>

src/Microsoft.Data.SqlClient/tests/FunctionalTests/Microsoft.Data.SqlClient.Tests.csproj

@@ -69,6 +69,7 @@
     <Compile Include="TestTdsServer.cs" />
     <Compile Include="SqlHelperTest.cs" />
     <Compile Include="..\..\src\Microsoft\Data\Common\MultipartIdentifier.cs" />
+    <Compile Include="SqlJsonTest.cs" />
   </ItemGroup>
   <!-- XUnit and XUnit extensions -->
   <ItemGroup>

src/Microsoft.Data.SqlClient/tests/FunctionalTests/SqlJsonTest.cs

@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+
+using Microsoft.Data.SqlTypes;
+using Xunit;
+
+namespace Microsoft.Data.SqlClient.Tests
+{
+    public class SqlJsonTest
+    {
+        [Fact]
+        public void SqlJsonTest_Null()
+        {
+            SqlJson json = new();
+            Assert.True(json.IsNull);
+        }
+    }
+}