Develop Reference

How to programmatically create a class library DLL using reflection?

Suppose my code possesses the knowledge about the metadata of a
nonexistent class library "mytest.dll", such as the types in this library, the functions of the types, the parameters and return types of the functions, etc.
How does my code manufacture this DLL using techniques such as reflection?
I know my code can generate the "mytest.cs" text file, then execute the compiler to produce the DLL, then delete the "mytest.cs" file. Just want to know if there are "more advanced" or "cooler" ways to do it.
Thanks.

There are 4 main steps in the process to compile and execute dynamic .net scripts from your application, even really complex scenarios can be simplified in this way:
Generate the code
Compile the script
Load the assembly
Execute the code
Lets generate a simple Hello Generated C# World App right now!:
Create a method that will generate an assembly that has 1 class called HelloWorldApp, this class has 1 method called GenerateMessage it will have X input parameters that will be integers, it will return a CSV string of the arguments that were passed in to it.
This solution requires the following package to be installed:
PM> Install-Package 'Microsoft.CodeAnalysis.CSharp.Scripting'
And will require the following using statements:
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.Emit;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;
Orchestration
The following method encapsulates the above steps:
private static void GenerateAndExecuteApp(int numberOfParameters)
{
string nameSpace = "Dynamic.Example";
string className = "HelloWorldApp";
string methodName = "GenerateMessage";
// 1. Generate the code
string script = BuildScript(nameSpace, className, methodName, numberOfParameters);
// 2. Compile the script
// 3. Load the Assembly
Assembly dynamicAssembly = CompileScript(script);
// 4. Execute the code
int[] arguments = Enumerable.Range(1, numberOfParameters).ToArray();
string message = ExecuteScript(dynamicAssembly, nameSpace, className, methodName, arguments);
Console.Out.WriteLine(message);
}
Generate the code
You say you already have item 1 sorted out, you can use StringBuilder, T4 templates or other mechanisms to generate the code files.
generating the code itself is its own question if you need help with that.
However, for our demo app, the following would work:
private static string BuildScript(string nameSpace, string className, string methodName, int numberOfParameters)
{
StringBuilder code = new StringBuilder();
code.AppendLine("using System;");
code.AppendLine("using System.Linq;");
code.AppendLine();
code.AppendLine($"namespace {nameSpace}");
code.AppendLine("{");
code.AppendLine($" public class {className}");
code.AppendLine(" {");
var parameterNames = Enumerable.Range(0, numberOfParameters).Select(x => $"p{x}").ToList();
code.Append($" public string {methodName}(");
code.Append(String.Join(",", parameterNames.Select(x => $"int {x}")));
code.AppendLine(")");
code.AppendLine(" {");
code.Append(" return $\"");
code.Append(String.Join(",", parameterNames.Select(x => $"{x}={{{x}}}")));
code.AppendLine("\";");
code.AppendLine(" }");
code.AppendLine(" }");
code.AppendLine("}");
return code.ToString();
}
For an input value of 3, the following code is generated:
using System;
using System.Linq;
namespace Dynamic.Example
{
public class HelloWorldApp
{
public string GenerateMessage(int p0,int p1,int p2)
{
return $"p0={p0},p1={p1},p2={p2}";
}
}
}
Compile the script (and Load it)
These are two discrete steps, however it is easiest to code them together in the same method, for this example we will ignore the generated dll and load the assembly directly into memory, that is generally the more likely use case for this type of scripting scenario anyway.
The hardest element of this is usually the referencing of the relevant dlls. There are a number of ways to achieve this, including loading all the dlls that are in the current executing context, I find a simple way to do this is to access the Assembly reference from the Type reference for the types we want to use inside the dynamic script:
List<string> dlls = new List<string> {
typeof(object).Assembly.Location,
typeof(Enumerable).Assembly.Location
};
Cut a long story short, this method compiles and loads the assembly into memory. It includes some crude compilation error handling, just to demonstrate how to do it:
private static Assembly CompileScript(string script)
{
SyntaxTree syntaxTree = CSharpSyntaxTree.ParseText(script);
// use "mytest.dll" if you want, random works well enough
string assemblyName = System.IO.Path.GetRandomFileName();
List<string> dlls = new List<string> {
typeof(object).Assembly.Location,
typeof(Enumerable).Assembly.Location
};
MetadataReference[] references = dlls.Distinct().Select(x => MetadataReference.CreateFromFile(x)).ToArray();
CSharpCompilation compilation = CSharpCompilation.Create(
assemblyName,
syntaxTrees: new[] { syntaxTree },
references: references,
options: new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary));
// Now we actually compile the script, this includes some very crude error handling, just to show you can
using (var ms = new MemoryStream())
{
EmitResult result = compilation.Emit(ms);
if (!result.Success)
{
IEnumerable<Diagnostic> failures = result.Diagnostics.Where(diagnostic =>
diagnostic.IsWarningAsError ||
diagnostic.Severity == DiagnosticSeverity.Error);
List<string> errors = new List<string>();
foreach (Diagnostic diagnostic in failures)
{
//errors.AddDistinct(String.Format("{0} : {1}", diagnostic.Id, diagnostic.Location, diagnostic.GetMessage()));
errors.Add(diagnostic.ToString());
}
throw new ApplicationException("Compilation Errors: " + String.Join(Environment.NewLine, errors));
}
else
{
ms.Seek(0, SeekOrigin.Begin);
return Assembly.Load(ms.ToArray());
}
}
}
Execute the code
Finally, we can use reflection to instantiate an instance of the new app and then we can obtain a reference to the method and it. The name of the parameters is irrelevant, as long
we pass them through in the correct order:
for this demo the order is sort of irrelevant to, given they are all the same type ;)
private static string ExecuteScript(Assembly assembly, string nameSpace, string className, string methodName, int[] arguments)
{
var appType = assembly.GetType($"{nameSpace}.{className}");
object app = Activator.CreateInstance(appType);
MethodInfo method = appType.GetMethod(methodName);
object result = method.Invoke(app, arguments.Cast<object>().ToArray());
return result as string;
}
Output
The final output from all this for our method with 3 passed into it is:
p0=1,p1=2,p2=3
So that was super crude, you can bypass most of the indirect reflection aspects through the use of Interfaces. If your generated script inherits from types or interfaces that the calling code also has a strong reference to, then ExecuteScript in the above example might look like this:
private static string ExecuteScript(Assembly assembly, string nameSpace, string className)
{
var appType = assembly.GetType($"{nameSpace}.{className}");
object app = Activator.CreateInstance(appType);
if (app is KnownInterface known)
{
return known.GenerateMessage(1,2,3);
}
throw new NotSupportedException("Couldn't resolve known type");
}
The major benefit to using an interface or base class reference is that you can natively set properties or call other methods without having to reflect references to them all or to resort to using dynamic which would work, but becomes a bit harder to debug.
Of course the interface solution is hard to implement when we had a variable number of parameters, so that's not the best example, usually with dynamic scripts you would construct a known environment, say a known class and methods, but you might want to inject custom code into the body of the method.
It's a bit of fun in the end, but this simple example shows that C# can be used as a runtime scripting engine without too much trouble.

C# TestProject - How do I get CodeFilePath & LineNumber for each test?

Given:
I have a project/solution containing tests. It is written in C# and is using nUnit.
What I want:
Somehow to retrieve all the tests in the Project/Solution without executing them and also giving me the CodeFilePath and LineNumber for each test.
What I tried / investigated:
dotnet test --list-tests : is giving me nothing (just the displayname)
NUnit3TestAdapter : is at somepoint exposing those values (see NUnitTestAdapter).
But how can I retrieve them?

Thanks #Charlie for pointing out a possible solution. I did basically exactly as you stated.
IMPORTANT NOTICE:
This seems to not work with dot.net CORE tests currently because of this issue: https://github.com/nunit/nunit-console/issues/710
Also DiaSession runs into an exception when used like this in dot.net CORE :-(
using System;
using System.Xml;
using Microsoft.VisualStudio.TestPlatform.ObjectModel;
using NUnit.Engine;
namespace ConsoleApp1
{
class Program
{
static void Main(string[] args)
{
var testAssemblyPath = #"C:\src\qata\src\tests\external\SomethingProject.Tests\bin\Debug\net461\SomethingProject.Tests.dll";
var package = new TestPackage(testAssemblyPath);
var testEngine = new TestEngine();
var runner = testEngine.GetRunner(package);
var nUnitXml = runner.Explore(TestFilter.Empty);
var session = new DiaSession(testAssemblyPath);
foreach (XmlNode testNode in nUnitXml.SelectNodes("//test-case"))
{
var testName = testNode.Attributes["fullname"]?.Value;
var className = testNode.Attributes["classname"]?.Value;
var methodName = testNode.Attributes["methodname"]?.Value;
var navigationData = session.GetNavigationData(className, methodName);
Console.WriteLine($"{testName} - {navigationData.FileName} - {navigationData.MinLineNumber}.");
}
}
}
}

Cannot get SyntaxTree from Compilation object

I'm a beginner of roslyn, so I tried to start learning it by making a very simple console application, which is introduced in the famous tutorial site. (https://riptutorial.com/roslyn/example/16545/introspective-analysis-of-an-analyzer-in-csharp), and it didn't work well.
The Cosole Application I made is of .NET Framework (target Framework version is 4.7.2), and not of .NET Core nor .NET standard.
I added the NuGet package Microsoft.CodeAnalysis, and Microsoft.CodeAnalysis.Workspaces.MSBuild, then wrote a simple code as I show below.
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.MSBuild;
using System;
using System.Linq;
namespace SimpleRoslynConsole
{
class Program
{
static void Main(string[] args)
{
// Declaring a variable with the current project file path.
// *** You have to change this path to fit your development environment.
const string projectPath =
#"C:\Users\[MyName]\Source\Repos\RoslynTrialConsole01\RoslynTrialConsole01.csproj";
var workspace = MSBuildWorkspace.Create();
var project = workspace.OpenProjectAsync(projectPath).Result;
// [**1]Getting the compilation.
var compilation = project.GetCompilationAsync().Result;
// [**2]As this is a simple single file program, the first syntax tree will be the current file.
var syntaxTree = compilation.SyntaxTrees.FirstOrDefault();
if (syntaxTree != null)
{
var rootSyntaxNode = syntaxTree.GetRootAsync().Result;
var firstLocalVariablesDeclaration = rootSyntaxNode.DescendantNodesAndSelf()
.OfType<LocalDeclarationStatementSyntax>().First();
var firstVariable = firstLocalVariablesDeclaration.Declaration.Variables.First();
var variableInitializer = firstVariable.Initializer.Value.GetFirstToken().ValueText;
Console.WriteLine(variableInitializer);
}
else
{
Console.WriteLine("Could not get SyntaxTrees from this projects.");
}
Console.WriteLine("Hit any key.");
Console.ReadKey();
}
}
}
My problem is that, SyntaxTrees property of Compilation object returns null in [**2]mark. Naturally, following FirstOrDefault method returns null.
I've tried several other code. I found I could get SyntaxTree from CSharp code text, by using CSharpSyntaxTree.ParseText method. But I couldn't get any from source code, by the sequence of
var workspace = MSBuildWorkspace.Create();
var project = workspace.OpenProjectAsync(projectPath).Result;
var compilation = project.GetCompilationAsync().Result;
What I'd like to know is if I miss something to get Syntax information from source code by using above process.
I'll appreciate someone give me a good advice.

I think the issue is that .net framework projects have their source files paths within their .csproj. And opening project works right away.
For .net core project you have no such information and, maybe, this is why Workspace instance doesn't know what to load and so loads nothing.
At least specifying .cs files as added documents does the trick. Try to apply this:
static class ProjectExtensions
{
public static Project AddDocuments(this Project project, IEnumerable<string> files)
{
foreach (string file in files)
{
project = project.AddDocument(file, File.ReadAllText(file)).Project;
}
return project;
}
private static IEnumerable<string> GetAllSourceFiles(string directoryPath)
{
var res = Directory.GetFiles(directoryPath, "*.cs", SearchOption.AllDirectories);
return res;
}
public static Project WithAllSourceFiles(this Project project)
{
string projectDirectory = Directory.GetParent(project.FilePath).FullName;
var files = GetAllSourceFiles(projectDirectory);
var newProject = project.AddDocuments(files);
return newProject;
}
}
Method WithAllsourceFiles will return you the project, compilation of which will in its turn have all syntax trees you would expect of it, as you would have in Visual Studio

MsBuildWorkspace won't work correctly unless you have all the same redirects in your app's app.config file that msbuild.exe.config has in it. Without the redirects, it's probably failing to load the msbuild libraries. You need to find the msbuild.exe.config file that is on your system and copy the <assemblyBinding> elements related to Microsoft.Build assemblies into your app.config. Make sure you place them under the correct elements configuration/runtime.

I searched various sample programs on the net and found the most reliable and safest method. The solution is to create a static method which returns SyntaxTrees in designated File as follow.
private static Compilation CreateTestCompilation()
{
var found = false;
var di = new DirectoryInfo(Environment.CurrentDirectory);
var fi = di.GetFiles().Where((crt) => { return crt.Name.Equals("program.cs", StringComparison.CurrentCultureIgnoreCase); }).FirstOrDefault();
while ((fi == null) || (di.Parent == null))
{
di = new DirectoryInfo(di.Parent.FullName);
fi = di.GetFiles().Where((crt) => { return crt.Name.Equals("program.cs", StringComparison.CurrentCultureIgnoreCase); }).FirstOrDefault();
if (fi != null)
{
found = true;
break;
}
}
if (!found)
{
return null;
}
var targetPath = di.FullName + #"\Program.cs";
var targetText = File.ReadAllText(targetPath);
var targetTree =
CSharpSyntaxTree.ParseText(targetText)
.WithFilePath(targetPath);
var target2Path = di.FullName + #"\TypeInferenceRewriter.cs";
var target2Text = File.ReadAllText(target2Path);
var target2Tree =
CSharpSyntaxTree.ParseText(target2Text)
.WithFilePath(target2Path);
SyntaxTree[] sourceTrees = { programTree, target2Tree };
MetadataReference mscorlib =
MetadataReference.CreateFromFile(typeof(object).Assembly.Location);
MetadataReference codeAnalysis =
MetadataReference.CreateFromFile(typeof(SyntaxTree).Assembly.Location);
MetadataReference csharpCodeAnalysis =
MetadataReference.CreateFromFile(typeof(CSharpSyntaxTree).Assembly.Location);
MetadataReference[] references = { mscorlib, codeAnalysis, csharpCodeAnalysis };
return CSharpCompilation.Create("TransformationCS",
sourceTrees,
references,
new CSharpCompilationOptions(
OutputKind.ConsoleApplication));
}
And the caller program will be like this.
static void Main(string[] args)
{
var test = CreateTestCompilation();
if (test == null)
{
return;
}
foreach (SyntaxTree sourceTree in test.SyntaxTrees)
{
Console.WriteLine(souceTree.ToFullString());
}
}
Of course, many improvements are needed to put it to practical use.

Retrieve TFS Test Steps always returns count of 0

I am trying to retrieve test steps (aka "actions") that have been added to a test case in TFS (2017.2) using the API (Microsoft.TeamFoundationServer.ExtendedClient v15.112.1). My current implementation always returns 0 test steps, although the actual test case has steps. I tried this as well in a clean new Team Project without any Work Item customization and even there it returns 0 steps. My implementation uses the older API (based on SOAP webservices), because it seems the newer http based API does not yet implement test steps. This is the code I have used:
private void GetTestStepsForTestCase(int testCaseId, int testSuiteId,
string teamProjectName, Uri tfsUrl)
{
TfsTeamProjectCollection tpc = new TfsTeamProjectCollection(tfsUrl);
ITestManagementService itms = tpc.GetService<ITestManagementService>();
ITestManagementTeamProject ittp = itms.GetTeamProject(teamProjectName);
ITestSuiteBase suite = ittp.TestSuites.Find(testSuiteId);
ITestCaseCollection testCaseCollection = suite.AllTestCases;
ITestCase itestCase = testCaseCollection.FirstOrDefault(t => t.Id == testCaseId);
foreach (Microsoft.TeamFoundation.TestManagement.Client.ITestAction itestAction in itestCase.Actions)
{
// Do something
}
}
Anyone?

You can use below sample to retrieve the test case steps from a specific test suite, it works on my side:
Install the nuget package : Microsoft.TeamFoundationServer.ExtendedClient - 15.112.1
using Microsoft.TeamFoundation.Client;
using Microsoft.TeamFoundation.TestManagement.Client;
using Microsoft.VisualStudio.Services.Client;
using System;
namespace RetrieveTestSteps
{
class Program
{
static void Main(string[] args)
{
var u = new Uri("http://server:8080/tfs/DefaultCollection");
var c = new VssClientCredentials();
TfsTeamProjectCollection tpc = new TfsTeamProjectCollection(u, c);
tpc.EnsureAuthenticated();
ITestManagementService itms = tpc.GetService<ITestManagementService>();
ITestManagementTeamProject ittp = itms.GetTeamProject("LCScrum");
ITestSuiteBase suite = ittp.TestSuites.Find(352);
ITestCaseCollection testCaseCollection = suite.AllTestCases;
foreach (var tc in testCaseCollection)
{
ITestCase testcase = ittp.TestCases.Find(tc.Id);
foreach (ITestAction action in testcase.Actions)
{
Console.WriteLine(String.Format("{0} - {1}", testcase.Id, action));
}
}
Console.Read();
}
}
}

OK, I finally figured out this one myself. The answer and comments of Andy helped me validate that my code is correct. I just discovered that my code worked fine when NOT debugging! When debugging, at some point I noticed this:
So probably because of lazy loading somewhere, it is not possible to verify the count of the attachments debug-time (see post here: Lazy<T>: "The function evaluation requires all threads to run").

Getting a SemanticModel of a cshtml file?

I'd like to use Roslyn to analyze semantic information within the context of a block of C# code inside a Razor View.
Is there any way (within Visual Studio 2015, or even in a unit test) to get the SemanticModel that represents this code?

Razor files contain a C# projection buffer with the generated C# code (including the parts that you don't write yourself). This buffer has full Roslyn services and is exactly what you're looking for.
You need to walk through the TextView's BufferGraph and find the CSharp buffer; you can then get its Document and semantic model.
If you're starting from the cursor location, you need simply need to map that location to a CSharp buffer.
Note that it is perfectly legal for a TextView to contain multiple CSharp buffers. (although the Razor editor will never do that)
If you aren't working in a TextView, you need to do all of this yourself; you need to run the Razor source through the Razor compiler to get the generated C# source, then compile that with Roslyn to get a semantic model.

Extract the code representing the view from the Razor view file using RazorTemplateEngine.GenerateCode and CSharpCodeProvider.GenerateCodeFromCompileUnit (or the VBCodeProvider if you want the intermediate source as VB.NET). You can then use Roslyn to parse the code.
There's an example of using Roslyn with Razor view files here.
Take note that GenerateCode carries a caveat:
This type/member supports the .NET Framework infrastructure and is not intended to be used directly from your code.

Just in case anyone else gets stuck on this, I have mini sample app which may help.
I had a CMS class like this:
public partial class CMS
{
public static string SomeKey
{
get { return (string) ResourceProvider.GetResource("some_key"); }
}
// ... and many more ...
}
... and I wanted to find out which of these were used throughout my solution for a report ... Enter Roslyn!
The following app will print out the count for the used and unused references:
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.FindSymbols;
using Microsoft.CodeAnalysis.MSBuild;
using Microsoft.CSharp;
using System;
using System.CodeDom.Compiler;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Web.Razor;
namespace TranslationSniffer
{
class Program
{
static void Main(string[] args)
{
new Program().Go().Wait();
}
public async Task Go()
{
// Roslyn!
var ws = MSBuildWorkspace.Create();
// Store the translation keys...
List<string> used = new List<string>();
List<string> delete = new List<string>();
string solutionRoot = #"C:\_Code\PathToProject\";
string sln = solutionRoot + "MySolution.sln";
// Load the solution, and find all the cshtml Razor views...
var solution = await ws.OpenSolutionAsync(sln);
var mainProj = solution.Projects.Where(x => x.Name == "ConsumerWeb").Single();
FileInfo[] cshtmls = new DirectoryInfo(solutionRoot).GetFiles("*.cshtml", SearchOption.AllDirectories);
// Go through each Razor View - generate the equivalent CS and add to the project for compilation.
var host = new RazorEngineHost(RazorCodeLanguage.Languages["cshtml"]);
var razor = new RazorTemplateEngine(host);
var cs = new CSharpCodeProvider();
var csOptions = new CodeGeneratorOptions();
foreach (var cshtml in cshtmls)
{
using (StreamReader re = new StreamReader(cshtml.FullName))
{
try
{
// Let Razor do it's thang...
var compileUnit = razor.GenerateCode(re).GeneratedCode;
// Pull the code into a stringbuilder, and append to the main project:
StringBuilder sb = new StringBuilder();
using (StringWriter rw = new StringWriter(sb))
{
cs.GenerateCodeFromCompileUnit(compileUnit, rw, csOptions);
}
// Get the new immutable project
var doc = mainProj.AddDocument(cshtml.Name + ".cs", sb.ToString());
mainProj = doc.Project;
}
catch(Exception ex)
{
Console.WriteLine("Compile fail for: {0}", cshtml.Name);
// throw;
}
continue;
}
}
// We now have a new immutable solution, as we have changed the project instance...
solution = mainProj.Solution;
// Pull out our application translation list (its in a static class called 'CMS'):
var mainCompile = await mainProj.GetCompilationAsync();
var mainModel = mainCompile.GetTypeByMetadataName("Resources.CMS");
var translations = mainModel.GetMembers().Where(x => x.Kind == SymbolKind.Property).ToList();
foreach (var translation in translations)
{
var references = await SymbolFinder.FindReferencesAsync(translation, solution) ;
if (!references.First().Locations.Any())
{
Console.WriteLine("{0} translation is not used!", translation.Name);
delete.Add(translation.Name);
}
else
{
Console.WriteLine("{0} :in: {1}", translation.Name, references.First().Locations.First().Document.Name);
used.Add(translation.Name);
}
}
Console.WriteLine();
Console.WriteLine("Used references {0}. Unused references: {1}", used.Count, delete.Count);
return;
}
}
}

Roslyn only models cshtml files while they are open, but during that time they are similar to every other source file in the Workspace model.
Is there something specific you have tried that isn't working?