C#

string name = "Smith, John";
string lastname = name.Substring(0, name.IndexOf(',')).Trim();
string firstname = name.Substring(name.IndexOf(',') + 1).Trim();

functFrm.MdiParent = this.MdiParent

private void butLogin_Click(object sender, EventArgs e){
    functFrm = new Functions();
    mf = new mainFrm();
    mf.ShowMdiChild(functFrm);
    this.Dispose();
}

public void ShowMdiChild(Form childForm)
{
    childForm.MdiParent = this;
    childForm.Show();
}

private void butLogin_Click(object sender, EventArgs e){

    functFrm = new Functions(txtUserName.Text, txtPassword.Text, p_host);
    functFrm.MdiParent = this.MdiParent;
    functFrm.Show();
}