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Xamarin iOS native linking failed for grpc.core

I've been attempting to make grpc work (ssl http2) on Xamarin Forms and after some pain I managed to get it to work on Android using Grpc.Core. However I couldn't get iOS to compile. Working through this problem I was trying to get anything grpc related to work on iOS, and eventually found the grpc experimental xamarin demo, HelloworldXamarin. Found here:
https://github.com/grpc/grpc/tree/master/examples/csharp/HelloworldXamarin
I downloaded the solution, but when I try to compile it I get the following errors:
Error Text:
Native linking failed, undefined symbol: operator delete(void*). Please verify that all the necessary frameworks have been referenced and native libraries are properly linked in.
Native linking failed. Please review the build log and the user flags provided to gcc: -LC:/g/examples/csharp/HelloworldXamarin/packages/Grpc.Core.2.23.0/build/Xamarin.iOS10/../../native/ios/universal -lgrpc_csharp_ext -force_load C:/g/examples/csharp/HelloworldXamarin/packages/Grpc.Core.2.23.0/build/Xamarin.iOS10/../../native/ios/universal/libgrpc_csharp_ext.a -LC:/g/examples/csharp/HelloworldXamarin/packages/Grpc.Core.2.23.0/build/Xamarin.iOS10/../../native/ios/universal -lgrpc -force_load C:/g/examples/csharp/HelloworldXamarin/packages/Grpc.Core.2.23.0/build/Xamarin.iOS10/../../native/ios/universal/libgrpc.a
linker command failed with exit code 1 (use -v to see invocation)
For the warning regarding not being able to find libgrpc_csharp_ext.a, I verified that the file was there.
There appears to be some issue with native linking, which I am very unfamiliar with. I'm using nearly the latest Visual Studio (well, 16.5.3), a mac build host with latest OS and XCode updated to latest. Didn't make any changes to the files pulled from git. I only just started working with Xamarin iOS this week, so everything should be in a fairly "default" state.
What could be wrong with my setup/system that makes this not work? I understand that this is an experimental feature still, but I can't tell if I've done something stupid or if there's been some change in something (like XCode? or it needing VS 2017?) that makes this no longer work? Is anyone else able to get this example to compile?
I've also tried newer versions of the grpc nuget packages and that only resulted in more errors.
Ultimately I'm trying to get latest Grpc.Core to work in iOS on Xamarin.Forms, though I have very little experience working with iOS. If there are issues with the latest versions of XCode/Visual Studio/Grpc.Core that are causing this, I'm willing to try to work through them, if someone can point me in the right direction.

It is not at all related to your versions or something that you did or didn't do.
First for some theory:
If someone wants to use Objective-C libraries or CocoaPods packages in their Xamarin project, they will need to create a binding library for this. Take it as some sort of a "bridge" between the native implementation and the later exposed C# code that you can use. You can learn more about the binding from the official documentation here and more specifically here.
To sum up the info - after the bindings have been created, you see a .lib or .a file. This is exactly what they have done - exposed some native code into the libgrpc_csharp_ext.a. Unfortunately, there are some bindings that are not correct. This is exactly what you are seeing here - the aftermath of an incorrect binding.
Looking a bit into the project I got to the following conclusions:
There is an open issue from May 2019 about this - https://github.com/grpc/grpc/issues/19172
Unfortunately, the issue is still active and there is no movement there.
I have confirmed that after version 1.21 (incl.) the build is not working. For now, you can downgrade to version 1.20.1 (last known to work). I have successfully built the solution with it. Please review the changelog and release notes for this specific version (if any) so that you know if it will fit your needs.
Basically, you have 2 options:
Downgrade to the last good version in order to use it;
If you want to use the latest version either wait for the issue to be fixed, or fork the repo and help with the fixing.
If you want to see their build script and help fix the issue, you can start from here.
Another useful resource is this video from the official Xamarin channel.

Unable to load "lpsolve55.dll" in VS2015 on 64-bits OS

For a project I am working on, I need to solve a mathematical model. I chose to do this using Microsoft.Solver.Foundation and the SolverFoundation.Plugin.LpSolve plugin. Both associated .dll files for these extension seem to work fine, as VS2015 recognizes and references them without a problem and compiles and runs my program without errors.
This is however up untill I try to actually solve my optimization, which needs "lpsolve55.dll" to work. I have downloaded this dll and put it in my project's bin/Debug folder, but for some kind of reason VS2015 just doesn't recognize it. I.e.
I can't reference it by simply browsing to it from my "Add Reference" tab.
It's impossible to (un-)register it via the regsvr32 cmd-prompt application, as it doesn't have any DLL (Un-)registry entry points.
The TlbImp.exe cmd-prompt application can't handle it.
So basically, after discovering the above (after trying the most-common internet solutions), I still feel quite dissatisfied to get the error message while I try to solve the optimization -
Unable to load DLL 'lpsolve55.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
The wierd part is also that I have another project in which I solve a similar problem, where there are absolutely no problems at all using lpsolve55.dll....
Some quick facts:
I reference .NET framwork 4.5.2. I have changed it to 4.5 as well as 4.0, but this didn't change anyting.
For as far as I can tell, the bin/debug folder of my projects are identical.
I am working on a fully updated windows 10 OS, 64 bits, while using visual studio 2015.
My question would thus be whether or not some of you have encountered a similar problem and if you were able to solve it in some way.
Highly appreciated!

After some careful analysis, I have found the answer to the problem. To be honest, as most things are, it was quite simple in the end. The lpsolve55.dll wasn't recognized because I didn't have my new bin-folder in the Path, which I did have with my old project. I simply forgot.
On a further note however, after the lpsolve55.dll directory was added to the path, I still got an error telling me there was no model to be found that could solve my directive. Since the error occured when I was calling the LPSolverDirective(), some research landed me on the following page:
http://lpsolve.sourceforge.net/5.5/MSF.htm
Above page gives a complete and stable way of how to acces lpsolve55.dll using the LPSolverPlugin straight out of Microsoft.Solver.Foundation.dll. After following the method in the link that involves editing my projects' bin/Debug and bin/Release folders, I got the LP model up and running within no-time.
Morale of the story - read the documentation. I am a bit of a beginner in programming entire multi-project solutions and using customly-added dlls, but hopefully this helps someone else experiencing the same. In the end, I learned a lot by simply trying different methods of getting it to work, so no time was wasted.

Installshield Limited Edition refuses to add Extended WPF Toolkit assemblies

I have had the pleasure of using ISLE and its now got to the point where I have to post a question on SO. Ohh the headache.
I have tried added the Extended WPF Tookit via nuget and manually to my application but with no luck getting ISLE to include these assemblies when it builds the installer. I have done a dependency scan in ISLE and in both scenario the dependencies are present.
I am using a TeamCity (v8.1.1) build server to automate the build. Everything works fine except that it will not include the above mentioned assemblies in the package.
How do I solve this problem?
Update #1
With some more research it seems that ISLE on the dev. box picked up a wrong version of log4net.dll while the build server found the correct version.
Resolution - Cleared all log4net.dll found in the "%temp%\Temporary asp.net files" folder.

You solve the problem by turning off dependency scanning and take responsibility for knowing what your applications needs to run and what the best way for deploying it. Dynamic installation authoring has never fully worked and it never will. When you take into consideration all the different kinds of apps and the way they take their dependencies it becomes obvious.
The easy button is an illusion.

I am unaware of why ISLE has these inconsistency and obvious logic problems however I have resolved my issue, albeit the solution is shaky.
Issue #1
Firstly I encountered a XamlParseException due to a TypedInitializationException. An assembly could not be loaded and that assembly was noted in the Exception which turned out to be log4net. The log4net assembly was in the folder however it was the wrong version.
Somehow ISLE found an older version of this assembly in the "%temp%\ASP.NET Temporary files" folder and used that in the package. Clear all these files and give ISLE no choice but to use the assembly you have provided. NOTE: Don't get gungho and delete the culprit assembly if found in the folder of one or more of your installed applications - it just might stop working.
Issue #2
I realized that not only were the Extended WPF Toolkit but the output of a dependent console application was missing from the install directory.
You would expect ISLE to find all dependencies however it doesn't.
Based on the advice provided by ##Christopher Painter I added the primary output of the console application dependency manually. I expected this to solve the console dependency issue however it turned out to solve both.
Now does ISLE break internally if the one of the dependencies is unavailable, locked, or some exception occurred while adding to the output causing it to stop at that point and not add any more dependencies. Who knows, but I am sure there are some flaws within ISLE Microsoft if you are going to ship a 3rd party and only a 3rd party installer ensure that it works properly first.
Update #1
Running the build a second time on the TeamCity server resulted in the Extended WPF Toolkit not being added again. So it seems again the ISLE installer is really shaky.
Issue #3
Another option to solve the missing Extended WPF Toolkit assemblies would have been to add then explicitly as dependencies. ISLE however adds a explicit rather than relative path location to these files meaning that you need to recreate the folder structure on your build server (not good).
If anyone has a better solution I would love to hear it. This request also goes out to Flexera Software and hopefully the answer is not to upgrade to the PRO version or pay for support.

SharpMap -Gdal Raster Layer, The type initializer for 'SharpMap.Layers.GdalRasterLayer' threw an exception [duplicate]

I started to use gdal_csharp dll in my application and read a geotiff file. but it says:
The type initializer for 'OSGeo.GDAL.GdalPINVOKE' threw an exception.
it's my code
string fileName = #"/path to geotiff file";
OSGeo.GDAL.Dataset DS =
OSGeo.GDAL.Gdal.Open(fileName, OSGeo.GDAL.Access.GA_ReadOnly);
can anyone help?
Edit:
I have these dlls
This is the full error message:
It says that cannot load gdal_wrap. But when I'm going to add that dll to my application the below message is shown:

As an update to this there is now GDAL maintained by the SharpMap team as a nuget package here which is updated regularly. You'll need to install both the "GDAL.Native" and "GDAL" package for your project to use the GDAL library. Once installed via nuget, they'll automatically create a "GdalConfiguration.cs" that you call into to initialize the GDAL paths before starting. The only thing to note is the packages are setup to automatically copy their appropriate GDAL libraries to your output build directory. If you need to deploy the application you'll have to do a bit of extra effort.

To solve this one I downloaded the prebuilt libraries as described here and grabbed FWTools from here.
The unmanaged DLLs I used came from \install_dir\FWTools2.4.7\bin and the C# wrapper from \install_dir\FWTools2.4.7\csharp.
gdal14.dll, msvcp71.dll and msvcr71.dll came from here, which is mentioned in that first link.
The error you are receiving re gdal_wrap.dll is referring to one of its dependencies. I threw that DLL into depends and it found a lengthy list of dependent libraries. Note that this list is likely longer due to my use of the FWTools distribution - if you built your version from source it may look different, though the same principles apply.
To get the above code to work on my machine I had the following files in my output directory:
gdal14.dll
gdalconst_csharp.dll
gdalconst_wrap.dll
gdal_csharp.dll
gdal_fw.dll
gdal_wrap.dll
geos_fw.dll
geotiff_fw.dll
hdf5dll.dll
hdf_fw.dll
jpeg12_osgeo.dll
jpeg_osgeo.dll
libcurl.dll
libeay32.dll
libexpat.dll
libmysql.dll
libpq.dll
libtiff_fw.dll
lti_dsdk_dll.dll
mfhdf_fw.dll
msvcp71.dll
msvcr71.dll
NCScnet_fw.dll
NCSEcw_fw.dll
NCSUtil_fw.dll
netcdf.dll
ogdi_32b1.dll
proj.dll
sqlite3.dll
ssleay32.dll
szlibdll.dll
xerces-c_2_7.dll
zlib1.dll
zlib_osgeo.dll
Now these don't necessarily all have to live in the output directory - as long as they are on your path somewhere (e.g., \Windows\System32) you should be fine.

I know it's an old question, but I believe my answer might help someone.
I was able to successfully compile and run examples using c# gdal by doing the following:
Downloading GDAL sdk from http://www.gisinternals.com/ (64 bit in my case)
Executing the SDKShell.bat script to set the system environment paths, etc.
Creating a project in Visual Studio. And referencing all .net dlls (the ones that names end with _csharp.dll), located in \bin\gdal\csharp\ inside downloaded SDK
Setting platform target in Visual Studio project settings to x64 to get rid og bad image format exceptions. The last step wouldn't be necessary if I'd choosse 32bit version of SDK to work with.
I did not install fwtools at all. It seems like the last build of fw_tools is relatively old, and sdk is still maintained.

I know this is a reasonably old question now, but I found this in google after researching the same problem myself, so this means that for searches on this error this is still a very relevant page to update given it's still in the top 5 from the big G when the same problem is searched.
In my case it was the answers from "DeusExMachina25" and "Grzegorz Sławecki" that struck a chord.
I'm writing some software that makes use of the current builds of "sharp map" on NUGet (as of 24th of June 2016) and my software kept throwing the same gdal_wrap message as the OP originally reported, even though I'm using the GDAL package provided by the Sharpmap team.
I didn't realize that the NUGet installer for the package had installed a configuration class for me, but after reading through this thread and finding out that it does I went looking for it.
Sure enough I found the file 'GdalConfiguration.cs' in my project and added a call to it in an appropriate place in my project, expecting GDAL to be initialized correctly.
However, after I did this, I still had the same problem.
So, I set a break point on the beginning of the GDAL routine that had been added, and waited until the break point was hit.
I then traced through the method, and eventually found the following line:
var gdalPath = Path.Combine(executingDirectory, "gdal");
at around line 64 in the file.
Tracing through this, I noticed that the path being built was:
d:\geodata\maptest\maptest\bin\debug\gdal
but the NUGet installer had installed all the dependent assemblies in
d:\geodata\maptest\maptest\bin\debug
Exactly where I expected them to be.
I changed line 64 so that it now read:
var gdalPath = Path.Combine(executingDirectory, "");
and voila, the error went away and everything started to work.
I could have done things the other way too, and created a folder called gdal, then copied everything into that, but that then would have gotten deleted when I did a "clean" on the project.
Since the config class, set's up various environment variables based on this path, quickly changing that one line also fixes up the path for the GDAL data files , plugins and a few other things too.

You could try using Dependency Walker to see if there are any dlls that gdal_csharp is trying to grab but cannot.

Have you added the path to your GDAL libraries to your PATH environment variable? I downloaded my files from http://vbkto.dyndns.org/sdk/?_sm_au_=iVVqjsHS2n46WP00 and here's my path: C:\libs\release-1600-gdal-1-9-mapserver-6-2\bin.

To use the C#-bindings of GDAL you need an installation of FWTools (from http://fwtools.maptools.org/) as well as the most current binaries that match your system (from http://vbkto.dyndns.org/sdk/). Afterwards it is important to include the bin-directory of FWTools (example for 64bit-systems: C:\Program Files (x86)\FWTools2.4.7\bin) in your PATH variable as well as the necessary dlls (gdal_csharp.dll was mentioned in the question) in your Visual Studio project references. I outlined the complete processs here.
This process works on 32 bit as well as 64 bit systems, I tested it with VS 2010 and 2012.

Remove the path to python from the system variables. Because the main gdal paths conflict with python 27

Did you forget to:
GdalConfiguration.ConfigureGdal();
GdalConfiguration.ConfigureOgr();
Gdal.AllRegister();
Ogr.RegisterAll();

In my case the issue was:
I had 2 projects in my solution: ProjectA and ProjectB
I was executing ProjectA, and ProjectA was referencing ProjectB
ProjectB is the one that contained the references to both GDAL and GDAL.Native
ProjectA tried to find GDAL.Native's files under ProjectA\bin\Debug\netcoreapp3.1\gdal ... but in reality those files are under ProjectB\bin\Debug\netcoreapp3.1\gdal
Possible solutions:
Dirty solution: just copy the files from ProjectB under ProjectA\bin\Debug\netcoreapp3.1
Okayish solution: add the GDAL.Native package to each one of your "entry projects"
I don't like either of those solutions. This stuff happens under GdalConfiguration.cs, so maybe there is a way to modify it to find the correct path.

Exception while using GDAL in C#

I started to use gdal_csharp dll in my application and read a geotiff file. but it says:
The type initializer for 'OSGeo.GDAL.GdalPINVOKE' threw an exception.
it's my code
string fileName = #"/path to geotiff file";
OSGeo.GDAL.Dataset DS =
OSGeo.GDAL.Gdal.Open(fileName, OSGeo.GDAL.Access.GA_ReadOnly);
can anyone help?
Edit:
I have these dlls
This is the full error message:
It says that cannot load gdal_wrap. But when I'm going to add that dll to my application the below message is shown:

As an update to this there is now GDAL maintained by the SharpMap team as a nuget package here which is updated regularly. You'll need to install both the "GDAL.Native" and "GDAL" package for your project to use the GDAL library. Once installed via nuget, they'll automatically create a "GdalConfiguration.cs" that you call into to initialize the GDAL paths before starting. The only thing to note is the packages are setup to automatically copy their appropriate GDAL libraries to your output build directory. If you need to deploy the application you'll have to do a bit of extra effort.

To solve this one I downloaded the prebuilt libraries as described here and grabbed FWTools from here.
The unmanaged DLLs I used came from \install_dir\FWTools2.4.7\bin and the C# wrapper from \install_dir\FWTools2.4.7\csharp.
gdal14.dll, msvcp71.dll and msvcr71.dll came from here, which is mentioned in that first link.
The error you are receiving re gdal_wrap.dll is referring to one of its dependencies. I threw that DLL into depends and it found a lengthy list of dependent libraries. Note that this list is likely longer due to my use of the FWTools distribution - if you built your version from source it may look different, though the same principles apply.
To get the above code to work on my machine I had the following files in my output directory:
gdal14.dll
gdalconst_csharp.dll
gdalconst_wrap.dll
gdal_csharp.dll
gdal_fw.dll
gdal_wrap.dll
geos_fw.dll
geotiff_fw.dll
hdf5dll.dll
hdf_fw.dll
jpeg12_osgeo.dll
jpeg_osgeo.dll
libcurl.dll
libeay32.dll
libexpat.dll
libmysql.dll
libpq.dll
libtiff_fw.dll
lti_dsdk_dll.dll
mfhdf_fw.dll
msvcp71.dll
msvcr71.dll
NCScnet_fw.dll
NCSEcw_fw.dll
NCSUtil_fw.dll
netcdf.dll
ogdi_32b1.dll
proj.dll
sqlite3.dll
ssleay32.dll
szlibdll.dll
xerces-c_2_7.dll
zlib1.dll
zlib_osgeo.dll
Now these don't necessarily all have to live in the output directory - as long as they are on your path somewhere (e.g., \Windows\System32) you should be fine.

I know it's an old question, but I believe my answer might help someone.
I was able to successfully compile and run examples using c# gdal by doing the following:
Downloading GDAL sdk from http://www.gisinternals.com/ (64 bit in my case)
Executing the SDKShell.bat script to set the system environment paths, etc.
Creating a project in Visual Studio. And referencing all .net dlls (the ones that names end with _csharp.dll), located in \bin\gdal\csharp\ inside downloaded SDK
Setting platform target in Visual Studio project settings to x64 to get rid og bad image format exceptions. The last step wouldn't be necessary if I'd choosse 32bit version of SDK to work with.
I did not install fwtools at all. It seems like the last build of fw_tools is relatively old, and sdk is still maintained.

I know this is a reasonably old question now, but I found this in google after researching the same problem myself, so this means that for searches on this error this is still a very relevant page to update given it's still in the top 5 from the big G when the same problem is searched.
In my case it was the answers from "DeusExMachina25" and "Grzegorz Sławecki" that struck a chord.
I'm writing some software that makes use of the current builds of "sharp map" on NUGet (as of 24th of June 2016) and my software kept throwing the same gdal_wrap message as the OP originally reported, even though I'm using the GDAL package provided by the Sharpmap team.
I didn't realize that the NUGet installer for the package had installed a configuration class for me, but after reading through this thread and finding out that it does I went looking for it.
Sure enough I found the file 'GdalConfiguration.cs' in my project and added a call to it in an appropriate place in my project, expecting GDAL to be initialized correctly.
However, after I did this, I still had the same problem.
So, I set a break point on the beginning of the GDAL routine that had been added, and waited until the break point was hit.
I then traced through the method, and eventually found the following line:
var gdalPath = Path.Combine(executingDirectory, "gdal");
at around line 64 in the file.
Tracing through this, I noticed that the path being built was:
d:\geodata\maptest\maptest\bin\debug\gdal
but the NUGet installer had installed all the dependent assemblies in
d:\geodata\maptest\maptest\bin\debug
Exactly where I expected them to be.
I changed line 64 so that it now read:
var gdalPath = Path.Combine(executingDirectory, "");
and voila, the error went away and everything started to work.
I could have done things the other way too, and created a folder called gdal, then copied everything into that, but that then would have gotten deleted when I did a "clean" on the project.
Since the config class, set's up various environment variables based on this path, quickly changing that one line also fixes up the path for the GDAL data files , plugins and a few other things too.

You could try using Dependency Walker to see if there are any dlls that gdal_csharp is trying to grab but cannot.

Have you added the path to your GDAL libraries to your PATH environment variable? I downloaded my files from http://vbkto.dyndns.org/sdk/?_sm_au_=iVVqjsHS2n46WP00 and here's my path: C:\libs\release-1600-gdal-1-9-mapserver-6-2\bin.

To use the C#-bindings of GDAL you need an installation of FWTools (from http://fwtools.maptools.org/) as well as the most current binaries that match your system (from http://vbkto.dyndns.org/sdk/). Afterwards it is important to include the bin-directory of FWTools (example for 64bit-systems: C:\Program Files (x86)\FWTools2.4.7\bin) in your PATH variable as well as the necessary dlls (gdal_csharp.dll was mentioned in the question) in your Visual Studio project references. I outlined the complete processs here.
This process works on 32 bit as well as 64 bit systems, I tested it with VS 2010 and 2012.

Remove the path to python from the system variables. Because the main gdal paths conflict with python 27

Did you forget to:
GdalConfiguration.ConfigureGdal();
GdalConfiguration.ConfigureOgr();
Gdal.AllRegister();
Ogr.RegisterAll();

In my case the issue was:
I had 2 projects in my solution: ProjectA and ProjectB
I was executing ProjectA, and ProjectA was referencing ProjectB
ProjectB is the one that contained the references to both GDAL and GDAL.Native
ProjectA tried to find GDAL.Native's files under ProjectA\bin\Debug\netcoreapp3.1\gdal ... but in reality those files are under ProjectB\bin\Debug\netcoreapp3.1\gdal
Possible solutions:
Dirty solution: just copy the files from ProjectB under ProjectA\bin\Debug\netcoreapp3.1
Okayish solution: add the GDAL.Native package to each one of your "entry projects"
I don't like either of those solutions. This stuff happens under GdalConfiguration.cs, so maybe there is a way to modify it to find the correct path.