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.

Revit IExternal Application Error- doesn't seems to run at all

Should we have something with the External application to properly register the event?
I also tried putting two breakpoints one inside the start module and other inside the Export module.
the first responded and waited for me to continue and the next didn't respond(hope did not run the line)
Also,I had manually tried coping the addin file to the addin location to avoid any post build event error but still doesnt seem to work.
could you tell me what I am I doing wrong here.
Here is the code :
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Autodesk.Revit.DB;
using Autodesk.Revit.UI;
using Autodesk.Revit.ApplicationServices;
using Autodesk.Revit.Attributes;
using Autodesk.Revit.UI.Events;
using Autodesk.Revit.DB.Events;
using System.IO;
namespace UserDataSheet
{
[Transaction(TransactionMode.Manual)]
[Regeneration(RegenerationOption.Manual)]
public class UserDataSheetclass : IExternalApplication
{
public Result OnShutdown(UIControlledApplication application)
{
return Result.Succeeded;
}
public Result OnStartup(UIControlledApplication application)
{
try
{
// Register event.
application.ControlledApplication.DocumentOpened += new EventHandler<Autodesk.Revit.DB.Events.DocumentOpenedEventArgs>(ExportLog);
return Result.Succeeded;
}
catch (Exception)
{
return Result.Failed;
}
}
public void ExportLog(object sender, DocumentOpenedEventArgs args)
{
var doc = sender as Document;
var isFamilyDoc = doc.IsFamilyDocument;
// variables to use
string RevitUserName = "";
DateTime OpenTime = new DateTime();
string localUserName = "";
string filename = "";
string filepath = "";
string content = "";
if (isFamilyDoc == false)
{
var IsloggedIn = Autodesk.Revit.ApplicationServices.Application.IsLoggedIn;
if (IsloggedIn == true )//&& doc.IsModelInCloud == true)
{
// use variables
filepath = doc.PathName;
filename = doc.Title;
RevitUserName = doc.Application.Username;
OpenTime = DateTime.Now;
localUserName = System.Environment.MachineName;
}
content = string.Format("Date and time : {0} \n Revit UserName : {1} \n Local PC UserName : {2} \n FileName : {3} \n FilePath : {4} "
, OpenTime.ToString(), RevitUserName, localUserName, filename, filepath);
TaskDialog.Show("Model Open Writer info", "user and file details : \n " + content);
}
var writefilepath = Path.GetTempPath();
var Writefile = writefilepath + "//records.txt";
FileStream fs = new FileStream(Writefile, FileMode.Append);
StreamWriter writer = new StreamWriter(fs);
writer.Write(content);
writer.Close();
File.OpenRead(Writefile);
}
}
}

First of all, you can completely remove the TransactionMode and RegenerationOption. The latter is completely obsolete and does nothing at all anywhere whatsoever. The former is only useful when declaring an external command. It is useless and ignored in the context of an external application.
Secondly, to address your question: you can set a breakpoint in the beginning of OnStartup. If the breakpoint is not hit, your add-in is not being loaded at all. Probably something is wrong with your add-in registration, e.g., in the add-in manifest *.addin file.
Go back to square one, i.e., work through the getting started material and the developer guide instructions on registering and loading a Revit add-in.

If the breakpoint in OnStartup is hit, then your add-in is loading correctly, which means that the add-in manifest *addin file is OK. So, you do not need to worry about that. The VisibilityMode tag is not used for external applications, by the way.

Thanks, Jeremy It worked
Firstly I apologies for adding this as answer( I don't know how to add codes in comment)
It worked when I deleted my Addin file and recreated it may be I had made some mistake in it.
meanwhile I have copied the following code from examples and used it,honestly I did't understand this line of the code.
"public void ExportLog(object sender, DocumentOpenedEventArgs args)"
can you point to a right source that explains this part. I have three questions here :
what object type is sender and args are they of type application?
How do I add a 3rd parameter to this method say I want the user to input a string to name the file the data is copied to.
Can I do this
var newEvent = new EventHandler<Autodesk.Revit.DB.Events.DocumentOpenedEventArgs>(ExportLog);
instead of
application.ControlledApplication.DocumentOpened += new EventHandler<Autodesk.Revit.DB.Events.DocumentOpenedEventArgs>(ExportLog);
why does all example use += is this to register the event every time a new instance of Revit is opened?
Thanks for your help.

You can see the class of sender yourself by setting a breakpoint at the beginning of ExportLog and looking in the debugger.
No, you cannot modify the signature of the event handler. It is predetermined by the Revit API.
Yes.
It sounds to me as if you might save some time and effort for yourself by learning a bit more about the basics of C# and .NET programming in general before continuing to tackle this task.

How to Convert C# Values to Node.js Object

I have simple C# object instantiated like
User theUser = new User("John", "Doe");
now I need to load it to my Node.js file like:
var theUser = {name:"John", lastName:"Doe"};
Can you please let me know how to do that? Do I have to save/write the output on a separate json file? or..?
Thanks

If you intend to use JSON as bridge from C# to Nodejs, use JavaScriptSerializer class to convert your C# class as JSON data.
https://msdn.microsoft.com/en-us/library/system.web.script.serialization.javascriptserializer.aspx
C#
// your data class
public class YourClassName
{
...
}
// Javascript serialization
using System.IO;
using System.Web.Script.Serialization;
String json = new JavaScriptSerializer().Serialize(YourClassName);
File.WriteAllText("json_file_path", json);
Node.js
// Async mode
var jsondata = require('fs').readFile('json_file_path', 'utf8', function (err, data) {
if (err) throw err; // throw error if not found or invalid
var obj = JSON.parse(jsondata);
});
// Sync mode
var jsondata = JSON.parse(require('fs').readFileSync('json_file_path', 'utf8'));
Node.js reference: How to parse JSON using Node.js?
Hopefully this is useful, CMIIW.

Why not just use Newtonsoft.Json - add a reference to this within your project.
To convert the object from a known type to json string;
string output = JsonConvert.SerializeObject(theUser);
To convert the object to a dynamic type;
dynamic json = JToken.Parse(theUser); - to dynamic
MSDN Link for extra help, if needed.

DLR: Do i really need code generation here?

spent some time again with the scripting interface of my app.
i guess i now have an advanced dlr problem here.
I have a python script
I have an .NET object [o1]
I call a method on the python script from .NET via Iron Python.
The python code creates an object [o2]
The python code calls an method on object [o1] passing [o2] as an argument (Via subclassing DynamicMetaObject)
In the .NET code of the o1-method i want to dynamically call methods on o2
For example i could do that via
((dynamic)o2).FuncInPythonScript
so far so good thats all working.
.NET calls Python (step 3)
Python calls back .NET (step 5)
So i have a basic biderectional control flow between .NET and Python.
We go further:
In the [o1]-method I use LanguageContext.GetMemberNames on [o2]
I wanna call these members somehow via reflection or expressions.
Meaning i dont wanna use the dynamic keyword as in step 7.
Instead somehow call the methods via reflection.
Problem is:
a) I do not know how to get the RuntimeType of the Python-Type, meaning i have no System.Reflection.MethodInfo so i stuck here
b) I try to use LanguageContext.CreateCallBinder and MetaObject.BindInvokeMember so i should have the method 'FuncInPythonScript' bound
But then i'm stuck in how to finally call the bound method.
I see i could use code generation to just generate the code as in step 7, just with the member names from step 8.
But is that really necessary?
I do not see wether approach a) or b) might work or maybe there is somthing i did not think of.
Please do not answer with basic "How do i invoke a python method from .NET" hints.
That is done in steps 1-7 and i have no problem doing this. It's really an advanced problem.
namespace DynamicMetaObjectTest
{
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
using System.Dynamic;
using System.Linq.Expressions;
using Microsoft.Scripting.Hosting;
using Microsoft.Scripting.Hosting.Providers;
class Program
{
internal sealed class CDotNetObject : IDynamicMetaObjectProvider
{
DynamicMetaObject IDynamicMetaObjectProvider.GetMetaObject(Expression aExp)
{
return new CInvoker(this, aExp);
}
private sealed class CInvoker : DynamicMetaObject
{
internal CInvoker(CDotNetObject aGws, Expression aExp) : base(aExp, BindingRestrictions.Empty, aGws)
{
this.DotNetObject = aGws;
}
private readonly CDotNetObject DotNetObject;
public override DynamicMetaObject BindGetMember(GetMemberBinder binder)
{
var aMethodInfo = this.GetType().GetMethod("GetSetResultDelegate");
var aExp = Expression.Call(Expression.Constant(this), aMethodInfo);
var aRestrictions = BindingRestrictions.GetTypeRestriction(this.Expression, this.LimitType);
var aMetaObject = new DynamicMetaObject(aExp, aRestrictions);
return aMetaObject;
}
public Action<object> GetSetResultDelegate()
{
return this.DotNetObject.SetResultProvider;
}
}
public void SetResultProvider(object aPythonObject_O2)
{
var aResult = ((dynamic)aPythonObject_O2).GetResult(); // this is for noobs. ;-)
var aMetaObjectProvider = (IDynamicMetaObjectProvider)aPythonObject_O2;
var aMetaObject = aMetaObjectProvider.GetMetaObject(Expression.Constant(aPythonObject_O2));
var aLanguageContext = HostingHelpers.GetLanguageContext(gScriptEngine);
var aMemberNames = aLanguageContext.GetMemberNames(aPythonObject_O2);
var aNonSystemMembers = from aMemberName in aMemberNames where !aMemberName.StartsWith("__") select aMemberName;
foreach (var aMemberName in aNonSystemMembers)
{
Console.WriteLine("Getting function result from Python script: " + aMemberName);
// Now problem:
// P1) How to determine wether its an function or an member variable?
// P2) How to invoke the method respectively get the value of the member variable?
// Your turn ;-)
// some of my failures:
{ // does not work:
//var aVar1Binder = aLanguageContext.CreateGetMemberBinder("GetVar1", false);
//var aVar1Bound = aMetaObject.BindGetMember(aVar1Binder);
//var aCallInfo = new CallInfo(0 , new string[]{});
//var aInvokeBinder = aLanguageContext.CreateCallBinder("GetVar1", false, aCallInfo);
//var aInvokeBound = aMetaObject.BindInvokeMember(aInvokeBinder, new DynamicMetaObject[]{ aVar1Bound});
////var aInvokeExp = Expression.Invoke(Expression.Constant(aInvokeBound), new Expression[] { });
}
{ // does not work
//var aExpandable = (IronPython.Runtime.Binding.IPythonExpandable)aMetaObject;
}
}
}
}
static ScriptEngine gScriptEngine;
static void Main(string[] args)
{
var aScriptRuntime = IronPython.Hosting.Python.CreateRuntime();
// That's the python script from step 1:
var aCode = "class CustomView(object) :" + Environment.NewLine +
"\tdef GetResult(self) :" + Environment.NewLine +
"\t\treturn 42;" + Environment.NewLine + // cuz 42 is the answer to everything ;-)
"DotNetObject.SetResultProvider(CustomView())";
var aEngine = aScriptRuntime.GetEngine("py");
gScriptEngine = aEngine;
var aScope = aEngine.CreateScope();
var aDotNetObject = new CDotNetObject();
aScope.SetVariable("DotNetObject", aDotNetObject);
// That's the invoke to pything from step 3:
aEngine.Execute(aCode, aScope);
}
}
}

Looking for Hello World program for Solr.NET in C#

I have Solr server running (on Linux box, not that it matter), it is loaded with 2M documents and search works fine in Java.
I need however to write C# (client) program to query it. I downloaded Solr.NET but I am confused what to begin with. Solutions included with it do not compile, and browsing through C# it does not look like the program is doing what I need to do.
Does anyone have a sort of Hello World program for Solr.NET in C#? Below I will publish Java version of what I and looking for, C# version anyone? Oh, and please, what minimum set of assemblies do I need to include into such simple client program? Thank you
import org.apache.solr.client.solrj.SolrQuery;
import org.apache.solr.client.solrj.SolrServer;
import org.apache.solr.client.solrj.impl.HttpSolrServer;
import org.apache.solr.client.solrj.response.QueryResponse;
import org.apache.solr.common.SolrDocumentList;
public class SolrHeloWorld // Java
{
public static void main(String[] args)
{
// Connect to server
SolrServer solr = new HttpSolrServer ("http://192.168.1.211:8983/solr/collection1");
// Query for search term 'banana'
SolrQuery query = new SolrQuery();
query.setQuery("banana");
query.setStart(0);
query.setRows(50);
query.set("defType", "edismax");
try
{
QueryResponse response = solr.query(query);
// Print results
SolrDocumentList results = response.getResults();
for (int i = 0; i < results.size(); i++)
{
System.out.println(results.get(i));
}
}
catch (Exception e)
{
System.out.println("Error: " + e.getMessage());
}
}
}

As suggested I have take another closer look at documentation for Solr.NET. Still, I wasn’t able to figure out which assemblies are missing in solutions that came with download so they still do not compile! More importantly it does not appear that you can write bare bone program that simply prints JSON without NHibernate, defining class mapping and all that.
Never the less, it is not that hard to write simple Hello World client program in C# that queries Solr. And it does not require Solr.NET at all! Here is the one that uses HttpWebRequest and JSON serializer/deserializer to simply print JSON of all documents returned by query
using System;
using System.Net;
using System.IO;
using System.Web.Script.Serialization; // Require adding System.Web.Extentions.dll
class SolrHeloWorld // C#
{
static void Main()
{
Uri uri = new Uri("http://192.168.1.211:8983/solr/collection1/select?q=banana&start=0&rows=50&wt=json&indent=true&defType=edismax");
WebRequest request = HttpWebRequest.Create(uri);
request.Method = WebRequestMethods.Http.Get;
WebResponse response = request.GetResponse();
StreamReader reader = new StreamReader(response.GetResponseStream());
string jsonResponse = reader.ReadToEnd();
response.Close();
JavaScriptSerializer serializer = new JavaScriptSerializer();
dynamic jsonObject = serializer.Deserialize<dynamic>(jsonResponse);
dynamic dd = jsonObject["response"]["docs"];
Object[] results = (Object[])dd;
foreach (Object res in results)
{
Console.WriteLine(serializer.Serialize(res));
}
}
}

There is a course in Pluralsight that gets you started with Solr and SolrNet. The last module is about SolrNet specifically:
http://www.pluralsight.com/courses/enterprise-search-using-apache-solr