feat: Serialize complex properties as JSON in Application Insights custom dimensions

Directory.Packages.props

@@ -7,6 +7,7 @@
   <ItemGroup Label="Runtime">
     <PackageVersion Include="Microsoft.ApplicationInsights" Version="2.23.0" />
     <PackageVersion Include="NLog" Version="5.5.0" />
+    <PackageVersion Include="System.Text.Json" Version="10.0.0" />
   </ItemGroup>
   <ItemGroup Label="Test">
     <PackageVersion Include="WireMock.Net" Version="1.6.9" />

src/NLogTarget/ApplicationInsightsTarget.cs

@@ -103,10 +103,10 @@
                 propertyBag.Add("LoggerName", logEvent.LoggerName);
             }
 
             if (logEvent.UserStackFrame != null)
             {
                 propertyBag.Add("UserStackFrame", logEvent.UserStackFrame.ToString());
                 propertyBag.Add("UserStackFrameNumber", logEvent.UserStackFrameNumber.ToString(CultureInfo.InvariantCulture));
             }
             else
             {
@@ -138,7 +138,7 @@
                         if (this.ExcludeProperties?.Contains(propertyKey) == true)
                             continue;
 
                         TryAddPropertyToPropertyBag(propertyBag, propertyKey, property.Value);
                     }
                 }
 
@@ -172,7 +172,9 @@
                 while (propertyBag.ContainsKey(propertyName));
             }
 
-            propertyBag[propertyName] = Convert.ToString(propertyValue, CultureInfo.InvariantCulture);
+            // Use StringDictionaryConverter to properly serialize complex objects to JSON
+            var converter = new StringDictionaryConverter(propertyBag);
+            converter[propertyName] = propertyValue;
         }
 
         /// <summary>

src/NLogTarget/NLogTarget.csproj

@@ -16,6 +16,7 @@
   <ItemGroup>
     <PackageReference Include="NLog" />
     <PackageReference Include="Microsoft.ApplicationInsights" />
+    <PackageReference Include="System.Text.Json" />
   </ItemGroup>
 
   <Import Project="..\CommonShared\CommonShared.projitems" Label="Shared" />

src/NLogTarget/StringDictionaryConverter.cs

@@ -10,6 +10,7 @@ namespace Microsoft.ApplicationInsights.NLogTarget
     using System;
     using System.Collections;
     using System.Collections.Generic;
+    using System.Text.Json;
 
     /// <summary>
     /// Converts from NLog Object-properties to ApplicationInsight String-properties
@@ -101,7 +102,31 @@ private static string SafeValueConverter(object value)
         {
             try
             {
-                return Convert.ToString(value, System.Globalization.CultureInfo.InvariantCulture);
+                if (value == null)
+                {
+                    return string.Empty;
+                }
+
+                // Handle primitive types and strings directly
+                if (value is string str)
+                {
+                    return str;
+                }
+
+                // Check if the value is a primitive type or a simple type that Convert.ToString handles well
+                var type = value.GetType();
+                if (type.IsPrimitive || type.IsEnum || value is decimal || value is DateTime || value is DateTimeOffset || value is Guid || value is TimeSpan)
+                {
+                    return Convert.ToString(value, System.Globalization.CultureInfo.InvariantCulture);
+                }
+
+                // For complex objects, serialize to JSON
+                return JsonSerializer.Serialize(value, new JsonSerializerOptions
+                {
+                    WriteIndented = false,
+                    PropertyNamingPolicy = null,
+                    DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.Never
+                });
             }
             catch
             {

src/NLogTarget/packages.lock.json

@@ -26,15 +26,38 @@
         "resolved": "5.5.0",
         "contentHash": "FCH8s7GWlonH5JXV9/EpeNJ8pRZQMVZOSWX3JrHPU8rzdHJhS5+lUGGvJIUOtzkGV1clYBFR0WXOI5FnUwVCMA=="
       },
+      "System.Text.Json": {
+        "type": "Direct",
+        "requested": "[10.0.0, )",
+        "resolved": "10.0.0",
+        "contentHash": "1Dpjwq9peG/Wt5BNbrzIhTpclfOSqBWZsUO28vVr59yQlkvL5jLBWfpfzRmJ1OY+6DciaY0DUcltyzs4fuZHjw==",
+        "dependencies": {
+          "Microsoft.Bcl.AsyncInterfaces": "10.0.0",
+          "System.Buffers": "4.6.1",
+          "System.IO.Pipelines": "10.0.0",
+          "System.Memory": "4.6.3",
+          "System.Runtime.CompilerServices.Unsafe": "6.1.2",
+          "System.Text.Encodings.Web": "10.0.0",
+          "System.Threading.Tasks.Extensions": "4.6.3"
+        }
+      },
+      "Microsoft.Bcl.AsyncInterfaces": {
+        "type": "Transitive",
+        "resolved": "10.0.0",
+        "contentHash": "vFuwSLj9QJBbNR0NeNO4YVASUbokxs+i/xbuu8B+Fs4FAZg5QaFa6eGrMaRqTzzNI5tAb97T7BhSxtLckFyiRA==",
+        "dependencies": {
+          "System.Threading.Tasks.Extensions": "4.6.3"
+        }
+      },
       "Microsoft.NETCore.Platforms": {
         "type": "Transitive",
         "resolved": "1.1.0",
         "contentHash": "kz0PEW2lhqygehI/d6XsPCQzD7ff7gUJaVGPVETX611eadGsA3A877GdSlU0LRVMCTH/+P3o2iDTak+S08V2+A=="
       },
       "System.Buffers": {
         "type": "Transitive",
-        "resolved": "4.5.1",
-        "contentHash": "Rw7ijyl1qqRS0YQD/WycNst8hUUMgrMH4FCn1nNm27M4VxchZ1js3fVjQaANHO5f3sN4isvP4a+Met9Y4YomAg=="
+        "resolved": "4.6.1",
+        "contentHash": "N8GXpmiLMtljq7gwvyS+1QvKT/W2J8sNAvx+HVg4NGmsG/H+2k/y9QI23auLJRterrzCiDH+IWAw4V/GPwsMlw=="
       },
       "System.Diagnostics.DiagnosticSource": {
         "type": "Transitive",
@@ -45,25 +68,53 @@
           "System.Runtime.CompilerServices.Unsafe": "5.0.0"
         }
       },
+      "System.IO.Pipelines": {
+        "type": "Transitive",
+        "resolved": "10.0.0",
+        "contentHash": "M1eb3nfXntaRJPrrMVM9EFS8I1bDTnt0uvUS6QP/SicZf/ZZjydMD5NiXxfmwW/uQwaMDP/yX2P+zQN1NBHChg==",
+        "dependencies": {
+          "System.Buffers": "4.6.1",
+          "System.Memory": "4.6.3",
+          "System.Threading.Tasks.Extensions": "4.6.3"
+        }
+      },
       "System.Memory": {
         "type": "Transitive",
-        "resolved": "4.5.4",
-        "contentHash": "1MbJTHS1lZ4bS4FmsJjnuGJOu88ZzTT2rLvrhW7Ygic+pC0NWA+3hgAen0HRdsocuQXCkUTdFn9yHJJhsijDXw==",
+        "resolved": "4.6.3",
+        "contentHash": "qdcDOgnFZY40+Q9876JUHnlHu7bosOHX8XISRoH94fwk6hgaeQGSgfZd8srWRZNt5bV9ZW2TljcegDNxsf+96A==",
         "dependencies": {
-          "System.Buffers": "4.5.1",
-          "System.Numerics.Vectors": "4.4.0",
-          "System.Runtime.CompilerServices.Unsafe": "4.5.3"
+          "System.Buffers": "4.6.1",
+          "System.Numerics.Vectors": "4.6.1",
+          "System.Runtime.CompilerServices.Unsafe": "6.1.2"
         }
       },
       "System.Numerics.Vectors": {
         "type": "Transitive",
-        "resolved": "4.4.0",
-        "contentHash": "UiLzLW+Lw6HLed1Hcg+8jSRttrbuXv7DANVj0DkL9g6EnnzbL75EB7EWsw5uRbhxd/4YdG8li5XizGWepmG3PQ=="
+        "resolved": "4.6.1",
+        "contentHash": "sQxefTnhagrhoq2ReR0D/6K0zJcr9Hrd6kikeXsA1I8kOCboTavcUC4r7TSfpKFeE163uMuxZcyfO1mGO3EN8Q=="
       },
       "System.Runtime.CompilerServices.Unsafe": {
         "type": "Transitive",
-        "resolved": "5.0.0",
-        "contentHash": "ZD9TMpsmYJLrxbbmdvhwt9YEgG5WntEnZ/d1eH8JBX9LBp+Ju8BSBhUGbZMNVHHomWo2KVImJhTDl2hIgw/6MA=="
+        "resolved": "6.1.2",
+        "contentHash": "2hBr6zdbIBTDE3EhK7NSVNdX58uTK6iHW/P/Axmm9sl1xoGSLqDvMtpecn226TNwHByFokYwJmt/aQQNlO5CRw=="
+      },
+      "System.Text.Encodings.Web": {
+        "type": "Transitive",
+        "resolved": "10.0.0",
+        "contentHash": "257hh1ep1Gqm1Lm0ulxf7vVBVMJuGN6EL4xSWjpi46DffXzm1058IiWsfSC06zSm7SniN+Tb5160UnXsSa8rRg==",
+        "dependencies": {
+          "System.Buffers": "4.6.1",
+          "System.Memory": "4.6.3",
+          "System.Runtime.CompilerServices.Unsafe": "6.1.2"
+        }
+      },
+      "System.Threading.Tasks.Extensions": {
+        "type": "Transitive",
+        "resolved": "4.6.3",
+        "contentHash": "7sCiwilJLYbTZELaKnc7RecBBXWXA+xMLQWZKWawBxYjp6DBlSE3v9/UcvKBvr1vv2tTOhipiogM8rRmxlhrVA==",
+        "dependencies": {
+          "System.Runtime.CompilerServices.Unsafe": "6.1.2"
+        }
       }
     }
   }

test/NLogTarget.Tests/NLogTargetTests.cs

@@ -19,7 +19,7 @@
 
     [TestClass]
     [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1001:TypesThatOwnDisposableFieldsShouldBeDisposable", Justification = "Disposing the object on the TestCleanup method")]
     public class ApplicationInsightsTargetTests
     {
         private AdapterHelper adapterHelper;
 
@@ -233,6 +233,88 @@
             Assert.AreEqual("Value", telemetry.Properties["Name"]);
         }
 
+        [TestMethod]
+        [TestCategory("NLogTarget")]
+        public void TraceHasComplexPropertiesSerializedAsJson()
+        {
+            var aiLogger = this.CreateTargetWithGivenConnectionString();
+
+            var complexObject = new
+            {
+                Name = "John Doe",
+                Age = 30,
+                Address = new
+                {
+                    Street = "123 Main St",
+                    City = "New York",
+                    ZipCode = "10001"
+                },
+                Tags = new[] { "tag1", "tag2", "tag3" }
+            };
+
+            var eventInfo = new LogEventInfo(LogLevel.Trace, "TestLogger", "Hello!");
+            eventInfo.Properties["ComplexObject"] = complexObject;
+            eventInfo.Properties["SimpleString"] = "SimpleValue";
+            aiLogger.Log(eventInfo);
+
+            var telemetry = this.adapterHelper.Channel.SentItems.FirstOrDefault() as TraceTelemetry;
+            Assert.IsNotNull(telemetry, "Didn't get the log event from the channel");
+
+            // Simple string should remain as is
+            Assert.AreEqual("SimpleValue", telemetry.Properties["SimpleString"]);
+
+            // Complex object should be serialized to JSON
+            Assert.IsTrue(telemetry.Properties.ContainsKey("ComplexObject"), "ComplexObject property not found");
+            var complexJson = telemetry.Properties["ComplexObject"];
+
+            // Verify it's JSON and contains expected properties
+            Assert.IsTrue(complexJson.Contains("\"Name\""), "JSON should contain Name property");
+            Assert.IsTrue(complexJson.Contains("\"John Doe\""), "JSON should contain Name value");
+            Assert.IsTrue(complexJson.Contains("\"Age\""), "JSON should contain Age property");
+            Assert.IsTrue(complexJson.Contains("30"), "JSON should contain Age value");
+            Assert.IsTrue(complexJson.Contains("\"Address\""), "JSON should contain Address property");
+            Assert.IsTrue(complexJson.Contains("\"Street\""), "JSON should contain nested Street property");
+            Assert.IsTrue(complexJson.Contains("\"123 Main St\""), "JSON should contain nested Street value");
+            Assert.IsTrue(complexJson.Contains("\"Tags\""), "JSON should contain Tags array");
+            Assert.IsTrue(complexJson.Contains("\"tag1\""), "JSON should contain array values");
+        }
+
+        [TestMethod]
+        [TestCategory("NLogTarget")]
+        public void TraceHandlesVariousPropertyTypes()
+        {
+            var aiLogger = this.CreateTargetWithGivenConnectionString();
+
+            var eventInfo = new LogEventInfo(LogLevel.Info, "TestLogger", "Testing various types");
+            eventInfo.Properties["String"] = "Simple string";
+            eventInfo.Properties["Int"] = 42;
+            eventInfo.Properties["Bool"] = true;
+            eventInfo.Properties["Decimal"] = 3.14m;
+            eventInfo.Properties["DateTime"] = new DateTime(2024, 1, 1, 12, 0, 0, DateTimeKind.Utc);
+            eventInfo.Properties["Array"] = new[] { 1, 2, 3 };
+            eventInfo.Properties["Dictionary"] = new Dictionary<string, object> { { "key1", "value1" }, { "key2", 123 } };
+            eventInfo.Properties["Null"] = null;
+
+            aiLogger.Log(eventInfo);
+
+            var telemetry = this.adapterHelper.Channel.SentItems.FirstOrDefault() as TraceTelemetry;
+            Assert.IsNotNull(telemetry, "Didn't get the log event from the channel");
+
+            // Simple types should be preserved as strings
+            Assert.AreEqual("Simple string", telemetry.Properties["String"]);
+            Assert.AreEqual("42", telemetry.Properties["Int"]);
+            Assert.AreEqual("True", telemetry.Properties["Bool"]);
+            Assert.IsTrue(telemetry.Properties["Decimal"].Contains("3.14"), "Decimal value should contain 3.14");
+
+            // Complex types should be serialized to JSON
+            Assert.IsTrue(telemetry.Properties["Array"].Contains("["), "Array should be JSON array");
+            Assert.IsTrue(telemetry.Properties["Array"].Contains("1"), "Array should contain values");
+            Assert.IsTrue(telemetry.Properties["Dictionary"].Contains("key1"), "Dictionary should be serialized");
+            Assert.IsTrue(telemetry.Properties["Dictionary"].Contains("value1"), "Dictionary should contain values");
+
+            // Null should be empty string
+            Assert.AreEqual(string.Empty, telemetry.Properties["Null"]);
+        }
 
         [TestMethod]
         [TestCategory("NLogTarget")]