private void ButtonAddingDog_Click(object sender, EventArgs e)
        {
            int?     x1, x2, x3;
            string   x4, x5, x6;
            double   x7;
            DateTime?x8;
            string   nullBreed    = textBoxIDBreed.Text,
                     nullIDMother = textBoxIDMother.Text,
                     nullIDFather = textBoxIDFather.Text,
                     nullDateBorn = textBoxDateBorn.Text;

            int?     nullBreed1    = (nullBreed == "" ? (int?)null : Convert.ToInt32(textBoxIDBreed.Text));
            int?     nullIDMother1 = (nullIDMother == "" ? (int?)null : Convert.ToInt32(textBoxIDMother.Text));
            int?     nullIDFather1 = (nullIDFather == "" ? (int?)null : Convert.ToInt32(textBoxIDFather.Text));
            DateTime?nullDateBorn1 = (nullDateBorn == ""? (DateTime?)null : Convert.ToDateTime(textBoxDateBorn.Text));


            Dog newdog = new Dog();

            if (textBoxDogName.Text != "")
            {
                if (textBoxColor.Text != "")
                {
                    if (textBoxGender.Text != "")
                    {
                        if (textBoxHeight.Text != "")
                        {
                            newdog.IDBreed  = (nullBreed1);
                            newdog.DogName  = textBoxDogName.Text;
                            newdog.Color    = textBoxColor.Text;
                            newdog.Gender   = textBoxGender.Text;
                            newdog.Height   = Convert.ToDouble(textBoxHeight.Text);
                            newdog.DateBorn = nullDateBorn1;
                            newdog.IDMother = nullIDMother1;
                            newdog.IDFather = nullIDFather1;
                            sql.AddDog(newdog);



                            x1 = nullBreed1;
                            x2 = nullIDMother1;
                            x3 = nullIDFather1;



                            x4 = textBoxDogName.Text;
                            x5 = textBoxColor.Text;
                            x6 = textBoxGender.Text;

                            x7 = Convert.ToDouble(textBoxHeight.Text);

                            x8 = nullDateBorn1;

                            MessageBox.Show(
                                "You added new dog:\n" +
                                "IDBreed: " + x1 + "\n" +
                                "Dog name: " + x4 + "\n" +
                                "Color: " + x5 + "\n" +
                                "Gender: " + x6 + "\n" +
                                "Height: " + x7 + "\n" +
                                "Date born: " + x8 + "\n" +
                                "ID Mother: " + x2 + "\n" +
                                "ID Father: " + x3 + "\n"
                                );
                        }
                        else
                        {
                            MessageBox.Show("Enter height");
                        }
                    }
                    else
                    {
                        MessageBox.Show("Enter gender");
                    }
                }
                else
                {
                    MessageBox.Show("Enter Dog color");
                }
            }
            else
            {
                MessageBox.Show("Enter Dog name");
            }
        }