C＃如何寫入文本文件？

Question

在線主題。 老師給了我們這個，但是沒有運行。 在第48行上引發錯誤，其中fileWriter.WriteLine為System.NullReferenceException：'對象引用未設置為對象的實例。

在線教程看起來完全不同

    public partial class frmMain : Form
    {
        private StreamWriter fileWriter;

        public class Record
        {
            public string Name { get; set; }
            public string ID { get; set; }
            public string Suburb { get; set; }
            public decimal Fee { get; set; }

        }

        string fileName = "student.txt";


        private void frmMain_Load(object sender, EventArgs e)
        {

            FileStream output = new FileStream(fileName,
                FileMode.OpenOrCreate, FileAccess.Write);

            fileWriter = new StreamWriter(output);
        }
        private void btnSave_Click(object sender, EventArgs e)
        {
            Record record = new Record();

            record.Name = txtName.Text;
            record.ID = txtID.Text;
            record.Suburb = txtSuburb.Text;
            record.Fee = Convert.ToDecimal(txtFee.Text);

            fileWriter.WriteLine(record.Name + "," + record.ID + "," +
                record.Suburb + "," + record.Fee); // Error here


            txtName.Text = "";
            txtID.Text = "";
            txtSuburb.Text = "";
            txtFee.Text = "";
        }

    }

Answer 1

您的frmMain_Load沒有連接，單擊IDE屬性中的load事件，然后選擇該方法。

添加了令人討厭的怪圈，供您欣賞