Creating Object from Class name specified in string

Question

I have a dropdownlist on a webpage which has list of all classnames , in C# code I need to instantiate object of selected items from dropdownlist and call method of it . All classes have similar methods .

 String sCalclationType = "N0059";
 var Calculator = Activator.CreateInstance("Calculator", sCalclationType ); 
 var count =  Calculator.DoCalculation();

I tried casting which shows "Cannot convert type 'System.Runtime.Remoting.ObjectHandle' to 'CypressDataImport.DiabetesHelper.NQF0059" , Also I need to cast to type which needs to be same as dropdown item so not sure how to do that .

//var calc = (N0059)Calculator;

How do I handle this scenario ?

Colin Smith · Accepted Answer · 2013-08-15 22:56:08Z

2

See here:

http://msdn.microsoft.com/en-us/library/d133hta4.aspx

Try this:

String sCalclationType = "N0059";
ObjectHandle handle = Activator.CreateInstance("Calculator", sCalclationType ); 
var Calculator = (N0059)handle.Unwrap();
var count = Calculator.DoCalculation();

or

String sCalclationType = "N0059";
ObjectHandle handle = Activator.CreateInstance("Calculator", sCalclationType );
Object p = handle.Unwrap();
Type t = p.GetType();
MethodInfo method = t.GetMethod("DoCalculation");
var count = method.Invoke(p, null);

answered Aug 15, 2013 at 22:56

Colin Smith

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2 Comments

user1649941 Over a year ago

In 1st method you are doing (N0059) cast but we dont know the type of class . Second method will work fine I think . Is it somehow possible to use 1st method by using inheriting all classes from some main class ?

Colin Smith Over a year ago

Yes. Create a base class that contains what all calculators should have...which I guess in your case is DoCalculation....and I guess a way to add terms.

Richard Vella · Accepted Answer · 2013-12-18 01:30:38Z

1

You need to return the wrapped object returned by the Activator.CreateInstace() method.

To do that have a look at ObjectHandle.Unwrap on MSDN.

Please also make sure you are using the fully qualified name of your type as explained here.

Below is an example of usage:

Object obj = Activator.CreateInstance(System.Reflection.Assembly.GetExecutingAssembly().FullName, "CypressDataImport.DiabetesHelper.NQF0059.N0059").Unwrap();
N0059 calculator= (N0059)obj;

edited Dec 18, 2013 at 1:30

answered Aug 15, 2013 at 22:57

Richard Vella

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