C# Convert dynamic string to existing Class [duplicate]

Question

Within a windows app, using C#, I have a reporting module that will be reliant upon classes to populate the reports. However there will be many reports and I do not want to have to code for each one.

The flow will be as such: Within the report editor, the report will be assigned a class (i.e. "Applications") as a string. When the user selected the report to run, the code will acquire the data from a SQL query. The code will take the data and find out which class to place the data into. Then the report will take the class and populate the report with the data from the class.

Here is my dilemna, how do I make the code dynamic so that the code will convert the assigned class into the proper Class Object?

Example in mind:

gVar = Report;
(gVar.ReportClass)oClass = new gVar.ReportClass;

Answer 1

Use Type.GetType (specifically one of the overloads (e.g., Type.GetType(string)) that takes a string parameter) to load the instance of Type for the appropriate class, and then use Activator.CreateInstance or Type.GetConstructor on that instance of Type to instantiate an instance.

So, something like

Type type = Type.GetType(assemblyQualifiedName);
object instance = Activator.CreateInstance(type);

Note that you must pass the assembly qualified name unless the type is in mscorlib or the currently executing assembly.

Additionally, Activator.CreateInstance assumes the existence of a default constructor. If there is not a default constructor, or you need to pass some parameters to the constructor, you will have to use an overload of Activator.CreateInstance that lets you specify the constructor parameters, or Type.GetConstructor to load the appropriate constructor.

Answer 2

You can use reflection to do it. If you give them all some similar base class or interface, you can do something like:

myBaseReport report = (myBaseReport)System.Activator.CreateInstance("MyAssemblyName", myClassStringWithFullNameSpace).Unwrap();

This will go into the assembly named and load the class directly. The class string is the full name of the type in question, so something like MyGlobalNamespace.MyCustomNameSpace.MySpecificType. This will allow you to create the specific type of report and put it into the base class type or interface type.