Create class from name

  • Thread starter Thread starter Peter Larsen [CPH]
  • Start date Start date
P

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
 
Peter said:
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.
Click to expand...
Activator.CreateInstance() should serve (almost) all your needs for dynamic
creation.
 
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
Click to expand...
 
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
Click to expand...
 
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

Delighting our customers is our #1 priority. We welcome your comments and
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Thank you all for your comments and thank you to you, Linda, for your great
samples.
You did it again :-)

BR
Peter
 
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