How to instantiate an object from a entity class name in string

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Hi,

I want to instantiate an object of a class whose name is arrived at the runtime.

var restlist = oContext.rests.ToList();
foreach(rest r in restlist)
{
     if (TableExists("bil" + r.code))
     {
           // want to instantiate an object of "bil"+r.code entity and access the 
           // properties of that class
     }
}

Is this possible this way in Entity Frawework ? Please suggest right way to do this. Thanks in advance.

What I have tried:

Tried use Activator.CreateInstance

String mfilename = "Test.bil" + r.code;
Object obj = Activator.CreateInstance(Type.GetType(mfilename));
// then here how to use this class and declare an object and get the properties

Posted 11-Jan-19 22:34pm

Priya-Kiko

Updated 11-Jan-19 23:12pm

v4

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2 solutions

Solution 2

Perhaps you are not specifying fullyqualified namespace of the class to be instantiated.

string formTypeFullName = string.Format("{0}.{1}", this.GetType().Namespace, "<class_name>"); 
		Type type = Type.GetType(formTypeFullName, true);
		object obj = Activator.CreateInstance(type);

Posted 11-Jan-19 23:12pm

AnkushK1

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OriginalGriff · Accepted Answer · 2019-01-11T23:10:00

Solution 1

Try this:

public class MyBaseClass
    {
    public int I;
    public string S;
    }
public class MyClass : MyBaseClass
    {
    ...
    }
private void MyButton_Click(object sender, EventArgs ew)
    {
    string myClassName = "GeneralTesting.frmMain+MyClass";
    Type t = Type.GetType(myClassName);
    MyBaseClass mbc = (MyBaseClass)Activator.CreateInstance(t);
    mbc.S = "hello";

Posted 11-Jan-19 23:10pm

OriginalGriff

Comments

Priya-Kiko 12-Jan-19 5:20am

Thank you for the response.

The class which im trying to instantiate is a table class (or entity class) created by Entity Framework. Which class am i supposed to use as BaseClass here ??

OriginalGriff 12-Jan-19 5:39am

That's the problem with dynamically creating types and trying to to use them from static code: unless you can provide a class to cast them to, you can't access properties, methods, fields, events, ... directly in code because you can't compile it, you need to use reflection to access them (which is slow, messy, and hard to read).
Remember, to access a class property directly in code, you need an instance of that class in an appropriately typed variable. In my example, if MyClass had a "Foo" property, you still couldn't access it via the mbc variable because not all types that can be in the variable will have a "Foo" property, they may have "Bar" instead.

It doesn't matter if this is EF or vanilla C#, unless you know what type it is at compile time (or use dynamic variables) you can't access the properties or methods except by reflection. (And dynamic only bypasses compile time checking, it will still fail if the instance doesn't have the property at run time.)

Priya-Kiko 12-Jan-19 6:50am

Ok. Thank you so much.

OriginalGriff 12-Jan-19 7:05am

You're welcome!