Create class from name

[Peter Larsen [CPH]]

Hi,

I can't remember how to write the code (in designtime) that constructs a
"unknown" class. I only have its base class - in designtime - not the exact
class.

The following code shows a sample of what i want to do:

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();

C1 c2 = CreateClass("C2");
C1 c3 = CreateClass("C3");
}

private C1 CreateClass(string classname)
{

return CreateTheClass(classname);
}
}

class C1
{ }
class C2 : C1
{ }
class C3 : C1
{ }

Please tell me how the method CreateClass() should look like.
Thank you in advance.

BR
Peter

 

[Jeroen Mostert]

I can't remember how to write the code (in designtime) that constructs a
"unknown" class. I only have its base class - in designtime - not the exact
class.

Activator.CreateInstance() should serve (almost) all your needs for dynamic
creation.

 

[Ilya Albrekht]

C1 c1 = new C1();

Hi,

I can't remember how to write the code (in designtime) that constructs a
"unknown" class. I only have its base class - in designtime - not the
exact
class.

The following code shows a sample of what i want to do:

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();

C1 c2 = CreateClass("C2");
C1 c3 = CreateClass("C3");
}

private C1 CreateClass(string classname)
{

return CreateTheClass(classname);
}
}

class C1
{ }
class C2 : C1
{ }
class C3 : C1
{ }

Please tell me how the method CreateClass() should look like.
Thank you in advance.

BR
Peter

 

[Ilya Albrekht]

Or you can use Activator.CreateInstance

Hi,

I can't remember how to write the code (in designtime) that constructs a
"unknown" class. I only have its base class - in designtime - not the
exact
class.

The following code shows a sample of what i want to do:

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();

C1 c2 = CreateClass("C2");
C1 c3 = CreateClass("C3");
}

private C1 CreateClass(string classname)
{

return CreateTheClass(classname);
}
}

class C1
{ }
class C2 : C1
{ }
class C3 : C1
{ }

Please tell me how the method CreateClass() should look like.
Thank you in advance.

BR
Peter

 

[Linda Liu[MSFT]]

Thanks Ilya and Jeroen for your replies!

Hi Peter,

As Ilya and Jeroen have suggested, a solution to create an instance from a
given class name is to call Activator.CreateInstance method. For example:

namespace WindowsApplication1
{
class C1
{ }
class C2 : C1
{ }
class C3 : C1
{ }

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
// pass the full name of the class
C1 c2 = CreateClass("WindowsApplication1.C2");
C1 c3 = CreateClass("WindowsApplication1.C3");
}

private C1 CreateClass(string classname)
{
ObjectHandle objh = Activator.CreateInstance(null, classname);
C1 obj = objh.Unwrap() as C1;
return obj;
}
}

Alternatively, you can get the Type from the given class name first and
then call the TypeDescriptor.CreateInstance method to create an instance of
the type. For example:

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
// pass the full name of the class
C1 c2 = CreateClass("WindowsApplication1.C2");
C1 c3 = CreateClass("WindowsApplication1.C3");
}

private C1 CreateClass(string classname)
{
C1 obj = null;
Type t = Type.GetType(classname, false);
if (t != null)
{
obj = TypeDescriptor.CreateInstance(null, t, null, null) as
C1;
}
return obj;
}
}

Hope this helps.
If you have any question, please feel free to let me know.

Sincerely,
Linda Liu
Microsoft Online Community Support

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[Peter Larsen [CPH]]

Thank you all for your comments and thank you to you, Linda, for your great
samples.
You did it again

BR
Peter