Deserialize custom dimensions from application insights API response.

Fixes Azure#13042

sdk/applicationinsights/Microsoft.Azure.ApplicationInsights.Query/src/Customized/Models/EventsResultDataCustomDimensions.cs

@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace Microsoft.Azure.ApplicationInsights.Query.Models
+{
+    public partial class EventsResultDataCustomDimensions
+    {
+#pragma warning disable CS0649 // Field is never assigned to, and will always have its default value
+        [JsonExtensionData]
+        private IDictionary<string, JToken> _customDimensionsValues;
+#pragma warning restore CS0649 // Field is never assigned to, and will always have its default value
+
+        public IEnumerable<string> Keys => _customDimensionsValues?.Keys;
+
+        public bool TryGetValue(string key, out string value)
+        {
+            if (_customDimensionsValues != null && _customDimensionsValues.TryGetValue(key, out var jToken))
+            {
+                value = jToken?.ToString();
+                return true;
+            }
+            value = null;
+            return false;
+        }
+    }
+}