How can I make a function to Add Control in C#

That's a little complex, because it depends to a large extent of what kind of parameter you want to pass: You need a parameter which tells you what type of control to create, which means passing it a string which is the class name, or a Type which indicates what type the control should be - and that's going to make your external code to call it complex - but how complex I can't tell.
Generally, this kind of aproach is not a good idea - it's possible, but that doesn't mean you should do it - it normally means your design is overcomplicated or badly thought out. There are exceptions though.

One way to do it is via generics:

private void CreateControl<T>() where T : Control, new()
    {
    T t = new T();
    Controls.Add(t);
    }

You then create the instance like this:

CreateControl<Button>();

Otherwise, it's parameter types and Reflection using Activator.CreateInstance[^]

Hello ,

Here is the sample code. Just take the combobox/Dropdown & list the control which you want to Create Dynamically & assign some value.
Take the Button to execute the code on Click.
For Example textbox as value 1,label as value 2
and Call Function CreateControl() & apply swith case.

Here is the small Code;
Take one integer as global variable

int cleft = 1; 

the variable is for the positioning purpose.

Then Modify your function CreateControl()

<pre lang="c#">private void CreateControl()
{
switch (urDropdown.selectedvaue)
                    {
                        case 1://TextBox
                            Button myButton = new Button();
                            this.Controls.Add(myButton);
                            myButton.Top = cleft * 25;
                            myButton.Left = 100;
                            myButton.Text = "TextBox " + this.cleft.ToString();
                            cleft++;
                            break;

                        case 2://LAbel
                            Label label1 = new Label();
                            this.Controls.Add(label1);
                            label1.Top = cleft * 25;
                            label1.Left = 100;
                            label1.Text = "label1 " + this.cleft.ToString();
                            cleft++;
                            break;
case 3://Button 
break;
                        default:
                    }

}


The code is for LAbel & Textbox.your expand it to any number of controls you want.You can take it for textbox,combobox,Groupbox,panel & so on .
Kindly take try, catch in your code to catch any error when it occurs.
Let me know whether this helped you or not.?
Happy Coding :-)