Windows .net form Not opening in Design view

clean the solution, check whether .aspx.cs name and .aspx page have same name ? buid again and check whether it works fine .if not working then,

it is better to take another form ,simply copy the design and paste in new form ,

Note: not clear if you are working in WinForms, ASP.NET, or ... ?

Most of the time I've had this problem, in WinForms, there was some corruption in the Designer.cs file.

If you have the older file you can open, and this is WinForms, suggest you do a comparison of the Designer.cs files between the new Form you can't open and the old Form.

Look for any differences.

best, Bill

may be your designer file is corrupted..,

check your <designer.cs> file

Which version of Visual Studio are you using and what is the exact message that is displayed. Newer versions of Visual Studio (2008 and 2010) are better at handling errors or giving some information on why they occurs. Half of the time Visual Studio 2008 or 2010 would give an hint where the error occurs.

Also, do you have multiple projects in your solution.

The first thing is effectively to clean the solution, close any designer, build (and run the application) and then open the designer again. If the form depend on another form, then try to open that form first. Sometime you also have to restart Visual Studio.

If you have done custom controls, then they might be bugged. In that case, you have to start another instance of Visual Studio to run the designer under a debugger so that you would be able to see what wrong with your code.

Typically if you have your own user control, you have to check if you are in design mode from the constructor or in Form_Load event if the code is somehow a bit complex. You would have to skip the code that does not make sense at design time.

In some complex projects, some forms are "hard" to open particulary when there are also C++ DLL and not all DLLs are up-to-date.

Also, you have to ensure that your reference are correct. One way would be top temporarily create a new form and add all controls that your are using in the form that cannot be opened.

Hi,

This could be the reason your Form control/User Control is typed

or

there might be any issue with control being as null, when opening in designer mode

YOu can add a code like

#if true

public class form : Form
{
}
#else

// Your existing code 

#endif

If you are seeing object null error, In constructor you can add a condition

protected bool IsInDesignMode
        {
            get
            {
                return this.GetService(typeof(System.ComponentModel.Design.IDesignerHost)) != null;
            }
        }