i need to retrieve username and password from SQL DB

i'm working on a school project that i need to retrieve username and password from sql database
and, depending on username and password entered, open specific windows form
i have administrator forms, managers,employees ETC.
I'm able to open the forms with this code but its not what i need cause itsnt surfing through the database
so far i havent make it work to surf the database(i guess i could but i just dont know how to open differents forms to specific username and password)
i have tried many things and needless to say none of them works
i tried with a FOR loop
as you may notice im new at programming i dont want to get it done i just want to learn
thanks for any input

private void buttonGo_Click(object sender, EventArgs e)
        {

           
            /*   //
               SqlConnection thisConnection1 = new SqlConnection(@"server=(local);Integrated security=true;" + "database=mydatabase");
               //
               SqlDataAdapter thisAdapter1 = new SqlDataAdapter("SELECT UserName,Password,Title FROM Login", thisConnection1);
               //
               SqlCommandBuilder thisbuilder1 = new SqlCommandBuilder(thisAdapter1);
               //
               DataSet thisdataset1 = new DataSet();   
               //
               thisAdapter1.Fill(thisdataset1, "Login");*/
               
                    if (TextBoxUsername.Text == "Mike" && TextBoxPassword.Text == "112")
            
                        {
                            Administration admin = new Administration();
                            admin.Visible = true;
                            admin.Activate();
                            TextBoxUsername.Clear();
                            TextBoxPassword.Clear();
                            this.Hide();
                            return;
                        }
               
                        if (TextBoxUsername.Text == "mike2" && TextBoxPassword.Text == "2012")
            
                        {
                            Admission admission = new Admission();
                            admission.Visible = true;
                            admission.Activate();
                            TextBoxUsername.Clear();
                            TextBoxPassword.Clear();
                            this.Hide();
                            return;
                        }
                            {
                            if (TextBoxUsername.Text == "mike3" && TextBoxPassword.Text == "2013")
                            { 
                                Discharge_Patients DisPa = new Discharge_Patients();
                                DisPa.Visible = true;
                                DisPa.Activate();
                                TextBoxUsername.Clear();
                                TextBoxPassword.Clear();
                                this.Hide();
                                return;
                            }
                                {
                                    if (TextBoxUsername.Text == "mike4" && TextBoxPassword.Text == "2011")
                            {
                                Patient_Report_List listPa = new Patient_Report_List();
                                listPa.Visible = true;
                                listPa.Activate();
                                TextBoxUsername.Clear();
                                TextBoxPassword.Clear();
                                this.Hide();
                                return;
                                    }
                                    {
                                        if (TextBoxUsername.Text == "mike5" && TextBoxPassword.Text == "2010")
                                        {
                                            Discharge_Patients DisPa = new Discharge_Patients();
                                            DisPa.Visible = true;
                                            DisPa.Activate();
                                            TextBoxUsername.Clear();
                                            TextBoxPassword.Clear();
                                            this.Hide();
                                            return;
                                        }
                                        }

                                    {
                                        if (TextBoxUsername.Text == "mike6" && TextBoxPassword.Text == "2009")
                                        {
                                            Discharge_Patients DisPa = new Discharge_Patients();
                                            DisPa.Visible = true;
                                            DisPa.Activate();
                                            TextBoxUsername.Clear();
                                            TextBoxPassword.Clear();
                                            this.Hide();
                                            return;
                                        }

                                    }
                                    {
                                        if (TextBoxUsername.Text == "mike6" && TextBoxPassword.Text == "2008")
                                        {
                                            Patient_Report_List DisPa = new Patient_Report_List();
                                            DisPa.Visible = true;
                                            DisPa.Activate();
                                            TextBoxUsername.Clear();
                                            TextBoxPassword.Clear();
                                            this.Hide();
                                            return;
                                        }

                                    }
                            
                            }

                }