Converting a string value that holds Form name to Form Type?

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Hi,

I have a table called tbllogin which has three columns username,password and Forrmname(which is of varchar type).I have a stored procedure which returns Formname based on UN and PWD.So i need to Show the form reurned byu the user.Please suggest me how to do this.

Regards
Chaithanya M

Posted 18-May-11 20:18pm

M.CHAITHANYA

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Programm3r · Answer 1 · 2011-05-18T20:24:00

Solution 1

Hi Chaithanya,

Why not make use of reflection? Have a look at the following:
Reflection (C# Programming Guide)
Reflection in C# Tutorial[^]

[UPDATE]

Okay, I have created two forms. From form1 I will make use of Reflection to call form2. Make use of the fully qualified name of the form. Thus, your proc must return the fully qualified name...

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        Assembly assem = Assembly.GetEntryAssembly();
        Form createInstance = (Form)Activator.CreateInstance(assem.GetType("WindowsFormsApplication1.Form2"));
        createInstance.ShowDialog();
    }
}

[UPDATE]

Kind regards,

Posted 18-May-11 20:24pm

Programm3r

Updated 18-May-11 21:30pm

v2

Comments

M.CHAITHANYA 19-May-11 2:47am

Hi,

I Have forms already created in my project .I just wanted to show them by pulling the formname from the database based on username and password

Programm3r 19-May-11 3:30am

I have updated the solution...

M.CHAITHANYA 19-May-11 8:17am

Hi,
-Will GetType method of assembly searches for the object provided by us?if so,will it implicitly casts to object type first and starts checking.?
-"CreateInstance"-the name some sounds like it is going to create another instance ,will thsi happen really.what exactly this method do?

Please comment on this.

Programm3r 19-May-11 9:16am

Hi,

Point #1:
---------

Yes, GetType gets the Type object with the specified name in the assembly instance.

The GetType() function is marked with the special attribute [MethodImpl(MethodImplOptions.InternalCall)]. This means its method body doesn't contain IL but instead is a hook into the internals of the .NET CLR. In this case, it looks at the binary structure of the object's metadata and constructs a System.Type object around it.

As far as I know, [MethodImpl(MethodImplOptions.InternalCall)] should be considered "magic" - you can't hook your own unmanaged code up to new functions with this attribute.

Point #2:
--------

"CreateInstance" -> Creates an instance of the specified type using that type's default constructor. Read more: http://msdn.microsoft.com/en-us/library/wccyzw83.aspx

Hope this answers your question...
Kind regards,

M.CHAITHANYA 19-May-11 9:32am

hi,
What exactly is creating an instance here.As the Form already exists,there is no need to create an instance right?

Regards
Chaithu

Programm3r 19-May-11 10:09am

Okay, so your original question was, to get hold of a WinForm object by a given name - this could be any form, right? (based on a username and password of course). Although the Form is within your project, how would you get hold of it during runtime? You would need an instance of that object, right?

Seeing that you don't have an instance of the object, you would need to create one. Hence, the Activator.CreateInstance method within my example...

Take the following into consideration:

void Form1_Button1_Click(object sender, EventArgs arg)
{
...
Form2 formTwo = new Form2(); // created a new instance of class Form2 - no instance existed before this line was executed
...
Form formThree = (Form)Activator.CreateInstance(assem.GetType("WindowsFormsApplication1.Form3")); // created a new instance of class Form3 - no instance existed before this line was executed
...
}

Does this answer your question...