How to fix 'The class Form1 can be designed, but is not the first class in the file'

Here’s how you can resolve this issue.

Visual Studio Form Render exception:

The class Form1 can be designed, but is not the first class in the file. Visual Studio requires that designers use the first class in the file. Move the class code so that it is the first class in the file and try loading the designer again.

Ensure that the class representing your form inherits from System.Windows.Forms.Form and is the first class declared in the file.

using System;
using System.Windows.Forms;

namespace YourNamespace
{
    public partial class YourForm : Form
    {        
        private void InitializeComponent()
        {
            // Auto-generated method for form initialization
        }
    }
}

Make sure YourForm is the first class immediately after the namespace declaration.

If you are using the partial keyword, ensure that all parts of the partial class are properly structured and that no conflicting definitions exist.

In Visual Studio, each form has a corresponding designer file (YourForm.Designer.cs) where the auto-generated code for the form’s controls and layout is stored.

If you have a form named Form1, your code file structure should look like this.

namespace YourNamespace
{
    public partial class Form1 : Form
    {
         public Form1()
         {
             InitializeComponent();
         }
    }
}

and Form1.Designer.cs

namespace YourNamespace
{
    public partial class Form1 : Form
    {
         /// <summary>
         /// Required designer variable.
         /// </summary>
         private System.ComponentModel.IContainer components = null;

         private void InitializeComponent(){
              this.components = new System.ComponentModel.Container();
              //....
         }
     }
}

If you have added some class or other code above the class definition in Form1.cs, you should remove that code.

By following these steps, you should be able to resolve the "The class Form1 can be designed, but is not the first class in the file" error in your Visual Studio.