Fix WebView.EvaluateJavaScriptAsync returning null on iOS for certain websites

src/Controls/tests/Core.UnitTests/WebViewExtensionsIOSTests.cs

@@ -0,0 +1,63 @@
+using Microsoft.Maui.Handlers;
+using Xunit;
+
+#if IOS
+using Foundation;
+using Microsoft.Maui.Platform;
+#endif
+
+namespace Microsoft.Maui.UnitTests
+{
+#if IOS
+	public class WebViewExtensionsIOSTests
+	{
+		[Fact]
+		public void HandleWKWebViewResult_NSNull_ReturnsNullString()
+		{
+			var result = WebViewExtensions.HandleWKWebViewResult(NSNull.Null);
+			Assert.Equal("null", result);
+		}
+
+		[Fact]
+		public void HandleWKWebViewResult_Null_ReturnsNullString()
+		{
+			var result = WebViewExtensions.HandleWKWebViewResult(null);
+			Assert.Equal("null", result);
+		}
+
+		[Fact]
+		public void HandleWKWebViewResult_NSString_ReturnsString()
+		{
+			var nsString = new NSString("Hello World");
+			var result = WebViewExtensions.HandleWKWebViewResult(nsString);
+			Assert.Equal("Hello World", result);
+		}
+
+		[Fact]
+		public void HandleWKWebViewResult_NSNumber_ReturnsNumberString()
+		{
+			var nsNumber = NSNumber.FromInt32(42);
+			var result = WebViewExtensions.HandleWKWebViewResult(nsNumber);
+			Assert.Equal("42", result);
+		}
+
+		[Fact]
+		public void HandleWKWebViewResult_NSNumberBoolean_ReturnsBooleanString()
+		{
+			var nsNumber = NSNumber.FromBoolean(true);
+			var result = WebViewExtensions.HandleWKWebViewResult(nsNumber);
+			Assert.Equal("True", result);
+		}
+
+		[Fact]
+		public void HandleWKWebViewResult_NSDictionary_ReturnsJSONString()
+		{
+			var dict = new NSMutableDictionary();
+			dict.SetValueForKey(new NSString("value"), new NSString("key"));
+			var result = WebViewExtensions.HandleWKWebViewResult(dict);
+			Assert.Contains("key", result);
+			Assert.Contains("value", result);
+		}
+	}
+#endif
+}

src/Controls/tests/TestCases.HostApp/Issues/Issue20288.xaml

@@ -0,0 +1,65 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="Maui.Controls.Sample.Issues.Issue20288"
+             Title="Issue 20288">
+    <ScrollView>
+        <StackLayout Padding="20">
+            <Label x:Name="InstructionLabel" 
+                   Text="This test validates that WebView.EvaluateJavaScriptAsync works correctly on iOS for various JavaScript result types." 
+                   Margin="0,0,0,20" />
+
+            <WebView x:Name="TestWebView" 
+                     HeightRequest="300"
+                     Source="https://httpbin.org/html" />
+
+            <Button x:Name="TestStringButton" 
+                    Text="Test String Result" 
+                    Clicked="OnTestStringClicked" 
+                    AutomationId="TestStringButton" />
+            <Label x:Name="StringResult" 
+                   Text="String result will appear here" 
+                   AutomationId="StringResult" />
+
+            <Button x:Name="TestNumberButton" 
+                    Text="Test Number Result" 
+                    Clicked="OnTestNumberClicked"
+                    AutomationId="TestNumberButton" />
+            <Label x:Name="NumberResult" 
+                   Text="Number result will appear here"
+                   AutomationId="NumberResult" />
+
+            <Button x:Name="TestBooleanButton" 
+                    Text="Test Boolean Result" 
+                    Clicked="OnTestBooleanClicked"
+                    AutomationId="TestBooleanButton" />
+            <Label x:Name="BooleanResult" 
+                   Text="Boolean result will appear here"
+                   AutomationId="BooleanResult" />
+
+            <Button x:Name="TestNullButton" 
+                    Text="Test Null Result" 
+                    Clicked="OnTestNullClicked"
+                    AutomationId="TestNullButton" />
+            <Label x:Name="NullResult" 
+                   Text="Null result will appear here"
+                   AutomationId="NullResult" />
+
+            <Button x:Name="TestObjectButton" 
+                    Text="Test Object Result" 
+                    Clicked="OnTestObjectClicked"
+                    AutomationId="TestObjectButton" />
+            <Label x:Name="ObjectResult" 
+                   Text="Object result will appear here"
+                   AutomationId="ObjectResult" />
+
+            <Button x:Name="TestInnerHTMLButton" 
+                    Text="Test innerHTML (Real World Case)" 
+                    Clicked="OnTestInnerHTMLClicked"
+                    AutomationId="TestInnerHTMLButton" />
+            <Label x:Name="InnerHTMLResult" 
+                   Text="innerHTML result will appear here"
+                   AutomationId="InnerHTMLResult" />
+        </StackLayout>
+    </ScrollView>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue20288.xaml.cs

@@ -0,0 +1,95 @@
+using System;
+using System.Threading.Tasks;
+using Microsoft.Maui.Controls;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 20288, "Evaluating javascript in MAUI WebView on IOS returns NULL", PlatformAffected.iOS)]
+	public partial class Issue20288 : ContentPage
+	{
+		public Issue20288()
+		{
+			InitializeComponent();
+		}
+
+		private async void OnTestStringClicked(object sender, EventArgs e)
+		{
+			try
+			{
+				var result = await TestWebView.EvaluateJavaScriptAsync("'Hello World'");
+				StringResult.Text = $"String: '{result ?? "NULL"}'";
+			}
+			catch (Exception ex)
+			{
+				StringResult.Text = $"Error: {ex.Message}";
+			}
+		}
+
+		private async void OnTestNumberClicked(object sender, EventArgs e)
+		{
+			try
+			{
+				var result = await TestWebView.EvaluateJavaScriptAsync("42");
+				NumberResult.Text = $"Number: '{result ?? "NULL"}'";
+			}
+			catch (Exception ex)
+			{
+				NumberResult.Text = $"Error: {ex.Message}";
+			}
+		}
+
+		private async void OnTestBooleanClicked(object sender, EventArgs e)
+		{
+			try
+			{
+				var result = await TestWebView.EvaluateJavaScriptAsync("true");
+				BooleanResult.Text = $"Boolean: '{result ?? "NULL"}'";
+			}
+			catch (Exception ex)
+			{
+				BooleanResult.Text = $"Error: {ex.Message}";
+			}
+		}
+
+		private async void OnTestNullClicked(object sender, EventArgs e)
+		{
+			try
+			{
+				var result = await TestWebView.EvaluateJavaScriptAsync("null");
+				NullResult.Text = $"Null: '{result ?? "NULL"}'";
+			}
+			catch (Exception ex)
+			{
+				NullResult.Text = $"Error: {ex.Message}";
+			}
+		}
+
+		private async void OnTestObjectClicked(object sender, EventArgs e)
+		{
+			try
+			{
+				var result = await TestWebView.EvaluateJavaScriptAsync("({name: 'test', value: 123})");
+				ObjectResult.Text = $"Object: '{result ?? "NULL"}'";
+			}
+			catch (Exception ex)
+			{
+				ObjectResult.Text = $"Error: {ex.Message}";
+			}
+		}
+
+		private async void OnTestInnerHTMLClicked(object sender, EventArgs e)
+		{
+			try
+			{
+				// Wait a bit for the page to load
+				await Task.Delay(2000);
+				var result = await TestWebView.EvaluateJavaScriptAsync("document.documentElement.innerHTML");
+				InnerHTMLResult.Text = result != null ? $"innerHTML length: {result.Length}" : "NULL";
+			}
+			catch (Exception ex)
+			{
+				InnerHTMLResult.Text = $"Error: {ex.Message}";
+			}
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue20288.cs

@@ -0,0 +1,63 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue20288 : _IssuesUITest
+	{
+		public Issue20288(TestDevice testDevice) : base(testDevice)
+		{
+		}
+
+		public override string Issue => "Evaluating javascript in MAUI WebView on IOS returns NULL";
+
+		[Test]
+		[Category(UITestCategories.WebView)]
+		public void WebViewEvaluateJavaScriptReturnsCorrectResults()
+		{
+			// Test String Result
+			App.WaitForElement("TestStringButton");
+			App.Tap("TestStringButton");
+			App.WaitForElement("StringResult");
+			var stringResult = App.FindElement("StringResult").GetText();
+			Assert.That(stringResult, Does.Contain("Hello World"), "String evaluation should return the correct string value");
+			Assert.That(stringResult, Does.Not.Contain("NULL"), "String evaluation should not return NULL");
+
+			// Test Number Result
+			App.Tap("TestNumberButton");
+			App.WaitForElement("NumberResult");
+			var numberResult = App.FindElement("NumberResult").GetText();
+			Assert.That(numberResult, Does.Contain("42"), "Number evaluation should return the correct number value");
+			Assert.That(numberResult, Does.Not.Contain("NULL"), "Number evaluation should not return NULL");
+
+			// Test Boolean Result
+			App.Tap("TestBooleanButton");
+			App.WaitForElement("BooleanResult");
+			var booleanResult = App.FindElement("BooleanResult").GetText();
+			Assert.That(booleanResult, Does.Contain("true"), "Boolean evaluation should return the correct boolean value");
+			Assert.That(booleanResult, Does.Not.Contain("NULL"), "Boolean evaluation should not return NULL");
+
+			// Test Null Result
+			App.Tap("TestNullButton");
+			App.WaitForElement("NullResult");
+			var nullResult = App.FindElement("NullResult").GetText();
+			Assert.That(nullResult, Does.Contain("NULL"), "Null evaluation should correctly return NULL");
+
+			// Test Object Result
+			App.Tap("TestObjectButton");
+			App.WaitForElement("ObjectResult");
+			var objectResult = App.FindElement("ObjectResult").GetText();
+			Assert.That(objectResult, Does.Contain("name"), "Object evaluation should return JSON representation");
+			Assert.That(objectResult, Does.Contain("test"), "Object evaluation should contain object values");
+			Assert.That(objectResult, Does.Not.Contain("NULL"), "Object evaluation should not return NULL");
+
+			// Test innerHTML (Real World Case) - this was the original failing case
+			App.Tap("TestInnerHTMLButton");
+			App.WaitForElement("InnerHTMLResult");
+			var innerHTMLResult = App.FindElement("InnerHTMLResult").GetText();
+			Assert.That(innerHTMLResult, Does.Not.Contain("NULL"), "innerHTML evaluation should not return NULL");
+			Assert.That(innerHTMLResult, Does.Contain("length:"), "innerHTML evaluation should return content with length");
+		}
+	}
+}

src/Core/src/Platform/iOS/WebViewExtensions.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Threading.Tasks;
+using Foundation;
 using WebKit;
 
 namespace Microsoft.Maui.Platform
@@ -77,7 +78,37 @@
 		static async Task<string> EvaluateJavaScript(WKWebView webView, string script)
 		{
 			var result = await webView.EvaluateJavaScriptAsync(script);
-			return result?.ToString() ?? "null";
+			return HandleWKWebViewResult(result);
+		}
+
+		internal static string HandleWKWebViewResult(NSObject? result)
+		{
+			if (result == null || result is NSNull)
+				return "null";
+
+			if (result is NSString nsString)
+				return nsString.ToString();
+
+			if (result is NSNumber nsNumber)
+				return nsNumber.ToString();
+
+			// For other types (NSDictionary, NSArray, etc.), use JSON serialization
+			// This matches the behavior that would come from JSON.stringify() on the web side
+			try
+			{
+				var jsonData = NSJSONSerialization.Serialize(result, NSJsonWritingOptions.PrettyPrinted, out var error);
+				if (error == null && jsonData != null)
+				{
+					var jsonString = NSString.FromData(jsonData, NSStringEncoding.UTF8);
+					return jsonString?.ToString() ?? "null";
+				}
+			}
+			catch
+			{
+				// Fall back to ToString if JSON serialization fails
+			}
+
+			return result.ToString() ?? "null";
 		}
 	}
 }