it-projekt/Form1.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;
using System.Text.Json;
using System.Windows.Forms;


namespace it_projekt
{
    public partial class Form1 : Form
    {

        private Database db = null;
        public Form1()
        {
            InitializeComponent();
            this.exportBtn.Enabled = false;
        }


        private void exportBtn_Click(object sender, EventArgs e)
        {
            if (jsonRBtn.Checked)
                export("All files (*.*)|*.*|json files (*.json)|*.json", "benutzer.json");
            else
                export("All files (*.*)|*.*|xml files (*.xml)|*.xml", "benutzer.xml");
        }

        private void loginBtn_Click(object sender, EventArgs e)
        {
            LoadUsersFromTable(this.userTxt.Text, this.passTxt.Text);
        }



        public void LoadUsersFromTable(string user, string password)
        {
            db = Database.getDatabase(user, password);
            if (db.Persons == null)
            {
                Database.resetDatabase();
                MessageBox.Show("Verbindung mit der Datenbank fehlgeschlagen :( \nVersuchen Sie es erneut.", "Datenbank Fehler!");
            }
            else
            {
                foreach (Person person in db.Persons)
                {
                    this.dataGrid.Rows.Add(person.Id, person.Firstname, person.Lastname, person.Department_short, person.Department_long, person.CreationDate, false);
                }
                this.loginBtn.Enabled = false;
            }
        }

        private void dataGrid_CellContentClick(object sender, DataGridViewCellEventArgs e)
        {

        }

        private System.EventHandler test()
        {
            this.exportBtn.Enabled = false;
            return null;
        }

        private void export(string Filter, string FileName)
        {
            List<Person> markedUsers = new List<Person>();
            foreach (DataGridViewRow row in dataGrid.Rows)
            {
                if (Convert.ToBoolean(row.Cells[6].Value))
                {
                    markedUsers.Add(db.Persons.Find(person => person.Id == row.Cells[0].Value.ToString()));
                }
            }
            if (markedUsers.Count == 0)
            {
                MessageBox.Show("Bitte wählen Sie mindestens eine Person zum exportieren aus!", "Exporter Error!");
                return;
            }

            Stream myStream;
            SaveFileDialog saveFileDialog1 = new SaveFileDialog();
            saveFileDialog1.Filter = Filter;
            saveFileDialog1.FilterIndex = 2;
            saveFileDialog1.RestoreDirectory = true;
            saveFileDialog1.FileName = FileName;
            if (saveFileDialog1.ShowDialog() == DialogResult.OK)
            {
                if ((myStream = saveFileDialog1.OpenFile()) != null)
                {
                    StreamWriter sw = new StreamWriter(myStream);
                    if (FileName.Contains("xml"))
                    {
                        var writer = new System.Xml.Serialization.XmlSerializer(typeof(List<Person>));
                        writer.Serialize(sw, markedUsers);
                    }
                    else //If xml is not selected, json is the only other option
                    {
                        string json = JsonSerializer.Serialize(markedUsers);
                        sw.Write(json);
                    }
                    sw.Flush();
                    sw.Close();
                    myStream.Close();
                }

            }
        }


        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void jsonRBtn_CheckedChanged(object sender, EventArgs e)
        {

        }

        private void xmlRBtn_CheckedChanged(object sender, EventArgs e)
        {

        }
        private void DataGridView_CellClick(object sender, DataGridViewCellEventArgs e)
        {
            //Check to ensure that the row CheckBox is clicked.
            if (e.RowIndex >= 0 && e.ColumnIndex == 6)
            {
                //Reference the GridView Row.
                DataGridViewRow row = dataGrid.Rows[e.RowIndex];

                //Set the CheckBox selection.
                row.Cells[6].Value = Convert.ToBoolean(row.Cells[6].EditedFormattedValue);
                exportBtn.Enabled = false;
                //If CheckBox is checked, display Message Box.
                if (Convert.ToBoolean(row.Cells[6].Value))
                {
                    exportBtn.Enabled = true;
                }
                foreach (DataGridViewRow r in dataGrid.Rows)
                {
                    if (Convert.ToBoolean(r.Cells[6].Value))
                    {
                        exportBtn.Enabled = true;
                    }
                }
            }
        }

    }
}