Throw exception in runtime When try to convert intptr to byte[]

[jingliancui]

Apple platform

iOS

Framework version

net9.0-*

Affected platform version

.Net 9 iOS

Description

Im trying to bind this :

var ptr = someintptr;
var versionStr = Marshal.PtrToStructure<byte[]>(ptr);

missing method exception will be thrown in runtime.

Steps to Reproduce

You can just try to using these codes in maui ios app to try.

Did you find any workaround?

No

Build logs

2025-06-15 23:59:10.070846+0800 SampleApp[12221:160812]
Unhandled Exception:
System.MissingMethodException: No parameterless constructor defined for type 'System.Byte[]'.
   at System.RuntimeType.CreateInstanceMono(Boolean nonPublic, Boolean wrapExceptions)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean wrapExceptions)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic, Boolean wrapExceptions)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Runtime.InteropServices.Marshal.PtrToStructure[Byte[]](IntPtr ptr)
   at GoogleMobileAdsBinding.Constants.get_GoogleMobileAdsVersionString() in /Users/ericcui/Desktop/GitHubWorkspace/iOSGoogleMobileAdsSDKBinding/12.6.0 2/GoogleMobileAdsBinding/Additions.cs:line 17
   at SampleApp.MainPage.ShowLibVersionButton_Clicked(Object sender, EventArgs e) in /Users/ericcui/Desktop/GitHubWorkspace/MAUIiOSGoogleMobileAdsSampleApp/src/SampleApp/MainPage.xaml.cs:line 39
   at Microsoft.Maui.Controls.Button.Microsoft.Maui.Controls.Internals.IButtonElement.PropagateUpClicked()
   at Microsoft.Maui.Controls.ButtonElement.ElementClicked(VisualElement visualElement, IButtonElement ButtonElementManager)
   at Microsoft.Maui.Controls.Button.SendClicked()
   at Microsoft.Maui.Controls.Button.Microsoft.Maui.IButton.Clicked()
   at Microsoft.Maui.Handlers.ButtonHandler.ButtonEventProxy.OnButtonTouchUpInside(Object sender, EventArgs e)
   at UIKit.UIControlEventProxy.Activated() in /Users/builder/azdo/_work/1/s/macios/src/UIKit/UIControl.cs:line 39
--- End of stack trace from previous location ---
   at ObjCRuntime.Runtime.ThrowException(IntPtr gchandle) in /Users/builder/azdo/_work/1/s/macios/src/ObjCRuntime/Runtime.cs:line 2831
   at UIKit.UIApplication.UIApplicationMain(Int32 argc, String[] argv, IntPtr principalClassName, IntPtr delegateClassName) in /Users/builder/azdo/_work/1/s/macios/src/UIKit/UIApplication.cs:line 75
   at UIKit.UIApplication.Main(String[] args, Type principalClass, Type delegateClass) in /Users/builder/azdo/_work/1/s/macios/src/UIKit/UIApplication.cs:line 107
   at SampleApp.Program.Main(String[] args) in /Users/ericcui/Desktop/GitHubWorkspace/MAUIiOSGoogleMobileAdsSampleApp/src/SampleApp/Platforms/iOS/Program.cs:line 13
2025-06-15 23:59:10.077152+0800 SampleApp[12221:160812] Unhandled managed exception: No parameterless constructor defined for type 'System.Byte[]'. (System.MissingMethodException)
   at System.RuntimeType.CreateInstanceMono(Boolean nonPublic, Boolean wrapExceptions)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean wrapExceptions)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic, Boolean wrapExceptions)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Runtime.InteropServices.Marshal.PtrToStructure[Byte[]](IntPtr ptr)
   at GoogleMobileAdsBinding.Constants.get_GoogleMobileAdsVersionString() in /Users/ericcui/Desktop/GitHubWorkspace/iOSGoogleMobileAdsSDKBinding/12.6.0 2/GoogleMobileAdsBinding/Additions.cs:line 17
   at SampleApp.MainPage.ShowLibVersionButton_Clicked(Object sender, EventArgs e) in /Users/ericcui/Desktop/GitHubWorkspace/MAUIiOSGoogleMobileAdsSampleApp/src/SampleApp/MainPage.xaml.cs:line 39
   at Microsoft.Maui.Controls.Button.Microsoft.Maui.Controls.Internals.IButtonElement.PropagateUpClicked()
   at Microsoft.Maui.Controls.ButtonElement.ElementClicked(VisualElement visualElement, IButtonElement ButtonElementManager)
   at Microsoft.Maui.Controls.Button.SendClicked()
   at Microsoft.Maui.Controls.Button.Microsoft.Maui.IButton.Clicked()
   at Microsoft.Maui.Handlers.ButtonHandler.ButtonEventProxy.OnButtonTouchUpInside(Object sender, EventArgs e)
   at UIKit.UIControlEventProxy.Activated() in /Users/builder/azdo/_work/1/s/macios/src/UIKit/UIControl.cs:line 39
--- End of stack trace from previous location ---
   at ObjCRuntime.Runtime.ThrowException(IntPtr gchandle) in /Users/builder/azdo/_work/1/s/macios/src/ObjCRuntime/Runtime.cs:line 2831
   at UIKit.UIApplication.UIApplicationMain(Int32 argc, String[] argv, IntPtr principalClassName, IntPtr delegateClassName) in /Users/builder/azdo/_work/1/s/macios/src/UIKit/UIApplication.cs:line 75
   at UIKit.UIApplication.Main(String[] args, Type principalClass, Type delegateClass) in /Users/builder/azdo/_work/1/s/macios/src/UIKit/UIApplication.cs:line 107
   at SampleApp.Program.Main(String[] args) in /Users/ericcui/Desktop/GitHubWorkspace/MAUIiOSGoogleMobileAdsSampleApp/src/SampleApp/Platforms/iOS/Program.cs:line 13
The program 'SampleApp.dll' has exited with code 0 (0x0).

[rolfbjarne]

var ptr = someintptr;
var versionStr = Marshal.PtrToStructure<byte[]>(ptr);

This won't work, because "byte[]" isn't a structure (among other things there's no way for Marshal.PtrToStructure to know how big the returned array should be).

If you want to create a byte array from an IntPtr, you can do something like this:

var ptr = Marshal.AllocHGlobal (256);
var span = new Span<byte> (ptr, 256);
var array = span.ToArray ();