how to open a second form only one time

Question

I have a program that content two form the first form is the main form and is the form that the program will start form it and the second form is the form that will show one time only to take to values and then will comeback to the first and the second will close note :in the start the program will do one from two

1. show second form if the values not in the program , then close the second and go to the first.
2. show the first and counties on it if the program have the values .

Note: when the second form will appear the first form will be hide , then after program takes the values from the user the second form will close and the first form will show

in anther word if the user give to the program the values from before the second form will not appear ,just the first form will appear only

the problem is the second form still open when the first form open after second form took the values

Code form 1

private void Form1_Load(object sender, EventArgs e)
{
    b();
}

private void b()
{
    Open();
    String SqlQuery = "SELECT * from test1";
    DataTable dt = new DataTable();
    dt = fetchData(SqlQuery);
    if (!(dt.Rows.Count >0))
    {
        MessageBox.Show("incorect user");
        fm2 = new Form2();                
        fm2.Show();
        this.Hide();
    }
}

code form2

public void fn()
{
    String SqlQuery = "SELECT * from test1 ";
    DataTable dt = new DataTable();
    dt = fetchData(SqlQuery);
    if (dt.Rows.Count > 0)
    {
        Application.OpenForms[0].Show();
        MessageBox.Show("DONE");
        this.Close();
    }
}

private void button1_Click(object sender, EventArgs e)
{
    string insertQuery = "INSERT INTO test1( name, phone) VALUES" +
        "('" + (textBox1.Text) + "','" + (textBox2.Text) + "')";

    ExcuteQuery(insertQuery);         
    fn();
}

And I have a question that is the form1 that I make it hide run in the background after the code Application.OpenForms[0].Show();

Answer 1

If not really looked in the details of your app. But if you do not want to open Form1 until Form2is closed, you should change:

fm2.Show();

to

fm2.ShowDialog();

Answer 2

if (!(dt.Rows.Count > 1))

change to

if (!(dt.Rows.Count >0))

Answer 3

You could try hiding the main form and then showing the second form as a dialog (which means the code flow goes to the second form until it's closed, then resumes where it left off). You could even do it in a loop, in case they close the second form without entering a user:

Form1

string SqlQuery = "SELECT * from test1 ";
DataTable dt = fetchData(SqlQuery);

while (dt.Rows.Count == 0)
{
    this.Hide(); 
    MessageBox.Show("No users exist. Please add one.");    

    using (Form2 fm2 = new Form2())
    {
        fm2.ShowDialog(this);
    }

    dt = fetchData(SqlQuery);
}

this.Show();

And then in the second form, you don't have to worry about trying to show the first form, because the first form will show itself when the code resumes.

Form2

if (dt.Rows.Count > 0)
{
    MessageBox.Show("User added successfully.");
    this.Close();
}
else
{
    MessageBox.Show("No user was added. Please try again.");
}

If you're still having an issue, then it seems like either fetchData or ExecuteQuery aren't working correctly. You should verify that a user is actually added to SQL after ExecuteQuery.

Also you can add a breakpoint in your code and examine the Count property of dt.Rows in the debugger to ensure that fetchData is working.