Well here is what I've written yesterday.
It is meant to be run in LinqPad, which is an awesome free tool to test linq queries or code snippets. (With an inexpensive upgrade to get intellisense)
The code should tell you how to deal with different kind of parameters (ref, out) and whether you are calling an instance method or not. (flip the comments in Main to test an instance method)
In LinqPad, you can use the Dump() extension method to let it show your objects in the results window. this is handy to see what is actually happening.
So, if you want to know how to dynamically construct a type and invoke it, this should get you started:
EDIT: I totally forgot to mention, that you do need to add these 2 namespaces to the query. You do that by hitting F4->additional namespace imports and adding these 2:
System.CodeDom.Compiler
System.CodeDom
public static String TestMethod1(int a, ref int X, out string t)
{
a += X;
X = a * 2;
t = "...>" + (X + a);
return a.ToString() + "...";
}
public class TestClass
{
public int SomeMethod(int a, DateTime? xyz)
{
if(xyz != null)
a+= xyz.GetValueOrDefault().Day;
return 12 + a;
}
}
void Main()
{
var sb = new StringBuilder();
var methodInfo = typeof(UserQuery).GetMethod("TestMethod1");
dynamic instance = CreateWrapper(methodInfo, sb);
instance.a = 11;
instance.X = 2;
instance.CallMethod();
/*
var methodInfo = typeof(TestClass).GetMethod("SomeMethod");
dynamic instance = CreateWrapper(methodInfo, sb);
instance.a = 11;
instance.xyz = new DateTime(2010, 1, 2);
instance.CallMethod(new TestClass());
*/
((Object)instance).Dump();
sb.ToString().Dump();
}
static object CreateWrapper(MethodInfo methodInfo, StringBuilder sb)
{
// pick either C#, VB or another language that can handle generics
var codeDom = CodeDomProvider.CreateProvider("C#");
var unit = new CodeCompileUnit();
var codeNameSpace = new CodeNamespace();
codeNameSpace.Name = "YourNamespace";
var wrapperType = AddWrapperType(codeDom, codeNameSpace, methodInfo, "WrapperType", "MethodResultValue");
unit.Namespaces.Add(codeNameSpace);
// this is only needed so that LinqPad can dump the code
codeDom.GenerateCodeFromNamespace(codeNameSpace, new StringWriter(sb), new CodeGeneratorOptions());
// put the temp assembly in LinqPad's temp folder
var outputFileName = Path.Combine(Path.GetDirectoryName(new Uri(typeof(UserQuery).Assembly.CodeBase).AbsolutePath),
Guid.NewGuid() + ".dll");
var results = codeDom.CompileAssemblyFromDom(new CompilerParameters(new[]{new Uri(methodInfo.DeclaringType.Assembly.CodeBase).AbsolutePath,
new Uri(typeof(UserQuery).Assembly.CodeBase).AbsolutePath,
new Uri(typeof(UserQuery).BaseType.Assembly.CodeBase).AbsolutePath}.Distinct().ToArray(),
outputFileName),
unit);
results.Errors.Dump();
new Uri(results.CompiledAssembly.CodeBase).AbsolutePath.Dump();
if(results.Errors.Count == 0)
{
var compiledType = results.CompiledAssembly.GetType(codeNameSpace.Name + "." + wrapperType.Name);
return Activator.CreateInstance(compiledType);
}
return null;
}
static CodeTypeDeclaration AddWrapperType(CodeDomProvider codeDom,
CodeNamespace codeNameSpace,
MethodInfo methodInfo,
string typeName,
string resultPropertyName)
{
var parameters = (from parameter in methodInfo.GetParameters()
select parameter).ToList();
var returnValue = methodInfo.ReturnType;
if(!String.IsNullOrEmpty(methodInfo.DeclaringType.Namespace))
codeNameSpace.Imports.Add(new CodeNamespaceImport(methodInfo.DeclaringType.Namespace));
var wrapperType = new CodeTypeDeclaration(typeName);
var defaultAttributes = MemberAttributes.Public | MemberAttributes.Final;
var thisRef = new CodeThisReferenceExpression();
Func<Type, Type> getRealType = t => t.IsByRef || t.IsPointer ? t.GetElementType(): t;
Func<String, String> getFieldName = parameterName => "m_" + parameterName + "_Field";
Action<ParameterInfo> addProperty = p =>
{
var realType = getRealType(p.ParameterType);
var usedName = p.Position == -1 ? resultPropertyName : p.Name;
wrapperType.Members.Add(new CodeMemberField
{
Name = getFieldName(usedName),
Type = new CodeTypeReference(realType),
Attributes= MemberAttributes.Private
});
var property = new CodeMemberProperty
{
Name = usedName,
Type = new CodeTypeReference(realType),
Attributes= defaultAttributes
};
property.GetStatements.Add(new CodeMethodReturnStatement(new CodeFieldReferenceExpression(thisRef,
getFieldName(usedName))));
property.SetStatements.Add(new CodeAssignStatement(new CodeFieldReferenceExpression(thisRef, getFieldName(usedName)),
new CodeArgumentReferenceExpression("value")));
wrapperType.Members.Add(property);
};
parameters.ForEach(addProperty);
if(methodInfo.ReturnParameter != null)
{
addProperty(methodInfo.ReturnParameter);
}
var callMethod = new CodeMemberMethod
{
Name="CallMethod",
Attributes=defaultAttributes
};
CodeMethodInvokeExpression invokeExpr;
if(!methodInfo.IsStatic)
{
callMethod.Parameters.Add(new CodeParameterDeclarationExpression(methodInfo.DeclaringType,
"instance"));
invokeExpr = new CodeMethodInvokeExpression(new CodeArgumentReferenceExpression("instance"),
methodInfo.Name);
}
else
invokeExpr = new CodeMethodInvokeExpression(new CodeTypeReferenceExpression(methodInfo.DeclaringType), methodInfo.Name);
foreach(var parameter in parameters)
{
CodeExpression fieldExpression = new CodeFieldReferenceExpression(thisRef,
getFieldName(parameter.Name));
if(parameter.ParameterType.IsByRef && !parameter.IsOut)
fieldExpression = new CodeDirectionExpression(FieldDirection.Ref, fieldExpression);
else if(parameter.IsOut)
fieldExpression = new CodeDirectionExpression(FieldDirection.Out, fieldExpression);
else if(parameter.IsIn)
fieldExpression = new CodeDirectionExpression(FieldDirection.In, fieldExpression);
invokeExpr.Parameters.Add(fieldExpression);
}
wrapperType.Members.Add(callMethod);
if(returnValue != typeof(void))
callMethod.Statements.Add(new CodeAssignStatement(new CodeFieldReferenceExpression(thisRef,
getFieldName(resultPropertyName)),
invokeExpr));
else
callMethod.Statements.Add(invokeExpr);
codeNameSpace.Types.Add(wrapperType);
return wrapperType;
}
