how can i call existing form from another existing from?

Hi, you have a button in form1 and want to open an another form on the click of that button but you want to hide/close the the form1 when an another form is opened am I right?
If this is the case then you double click on the button in form1 and wite the below code in the button click event
private void button1_Click(object sender,EventArgs e)
{
 Form2 obj=new Form2();
obj.Show();
}
and in form2's load event write the below code
private void Form2_Load(object sender, EventArgs e)
{
   Form1.ActiveForm.Close();
}
 
if you want to pass some values from form1 to form2 then you can go for overloaded constructor like below
 
private void button1_Click(object sender,EventArgs e)
{
string val1="sachi";
string val2="vasishta";
 
 Form2 obj=new Form2(val1,val2);
obj.Show();
}
 
and in form2's constructor you write the below code
public string assval1,assval2;
public Form2(string recval1,string recval2)
        {
            InitializeComponent();
             assval1=recval1;
             assval2=recval2;
        }
now you can use these two variables assval1,assval2 anywhere in form2.
try this