mscorlib.dll中发生未处理的“System.ArgumentNullException”类型异常附加信息：路径不能为null

Question

当我在图片框中的图片为空时尝试向数据库添加数据时出现此错误，但当图片框中包含图像时，系统运行良好。

错误：

  

发生了类型为“System.ArgumentNullException”的未处理异常   在mscorlib.dll中

     

其他信息：路径不能为空。

指出错误：

  

fsStream = new FileStream（this.imagePath，FileMode.Open，   FileAccess.Read）;

以下是我正在使用的代码：

Random _random = new Random();
        Timer _timer = new Timer();
        Wait _wait = new Wait();

        FileStream fsStream;
        BinaryReader bReader;

        byte[] imageByte = null;

        string imagePath;

        string gender;

        string connectionString = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=..\db1.accdb";

private void button1_Click(object sender, EventArgs e)
        {
            using (OpenFileDialog dlg = new OpenFileDialog())
            {
                dlg.Title = "Open Image";
                dlg.Filter = "JPG Files (*.jpg)|*.jpg|PNG Files (*.png)|*.png|All Files (*.*)|*.*";

                if (dlg.ShowDialog() == DialogResult.OK)
                {
                    pictureBox1.Image = new Bitmap(dlg.FileName.ToString());
                    imagePath = dlg.FileName;
                }
            }
        }


public virtual void button2_Click(object sender, EventArgs e)
        {
            fsStream = new FileStream(this.imagePath, FileMode.Open, FileAccess.Read);
            bReader = new BinaryReader(fsStream);
            imageByte = bReader.ReadBytes((int)fsStream.Length);

            if (this.pictureBox1.Image == null || this.textBox2.Text == "" || this.textBox3.Text == "" || this.textBox4.Text == "" || this.textBox5.Text == "")
            {
                System.Media.SoundPlayer _sound = new System.Media.SoundPlayer(@"C:\Windows\Media\Windows Exclamation.wav");
                _sound.Play();

                DialogResult _dialogResult = MessageBox.Show("Cannot Submit!", "Warning", MessageBoxButtons.OK);
            }

            else if (this.label9.Visible == false)
            {
                System.Media.SoundPlayer _sound = new System.Media.SoundPlayer(@"C:\Windows\Media\Windows Exclamation.wav");
                _sound.Play();

                DialogResult _dialogResult = MessageBox.Show("You have to check the Student ID before proceeding!", "Warning", MessageBoxButtons.OK);
            }

            else if (this.label8.Visible == true)
            {
                System.Media.SoundPlayer _sound = new System.Media.SoundPlayer(@"C:\Windows\Media\Windows Exclamation.wav");
                _sound.Play();

                DialogResult _dialogResult = MessageBox.Show("You cannot use this Student ID. Please Get another Student ID instead!", "Warning", MessageBoxButtons.OK);
            }

            else if (this.label7.Visible == true)
            {
                System.Media.SoundPlayer _sound = new System.Media.SoundPlayer(@"C:\Windows\Media\Windows Exclamation.wav");
                _sound.Play();

                DialogResult _dialogResult = MessageBox.Show("Student ID is being verified! Please wait!", "Warning", MessageBoxButtons.OK);
            }

            else
            {
                using (OleDbConnection conn = new OleDbConnection(connectionString))
                {
                    string query = "INSERT INTO [Student] ([StudentID], [FirstName], [LastName], [Photo], [DateOfBirth], [Address], [JoinedDate], [Class], [Gender]) VALUES (@StudentID, @FirstName, @LastName, @Photo, @DateOfBirth, @Address, @JoinedDate, @Class, @Gender)";

                    conn.Open();

                    using (OleDbCommand cmd = new OleDbCommand(query, conn))
                    {
                        cmd.Parameters.Add("@StudentID", System.Data.OleDb.OleDbType.VarChar);
                        cmd.Parameters["@StudentID"].Value = this.textBox1.Text;

                        cmd.Parameters.Add("@FirstName", System.Data.OleDb.OleDbType.VarChar);
                        cmd.Parameters["@FirstName"].Value = this.textBox2.Text;

                        cmd.Parameters.Add("@LastName", System.Data.OleDb.OleDbType.VarChar);
                        cmd.Parameters["@LastName"].Value = this.textBox3.Text;

                        cmd.Parameters.Add("@Photo", System.Data.OleDb.OleDbType.LongVarBinary);
                        cmd.Parameters["@Photo"].Value = imageByte;

                        cmd.Parameters.Add("@DateOfBirth", System.Data.OleDb.OleDbType.VarChar);
                        cmd.Parameters["@DateOfBirth"].Value = this.dateTimePicker1.Text;

                        cmd.Parameters.Add("@Address", System.Data.OleDb.OleDbType.VarChar);
                        cmd.Parameters["@Address"].Value = this.textBox4.Text;

                        cmd.Parameters.Add("@JoinedDate", System.Data.OleDb.OleDbType.VarChar);
                        cmd.Parameters["@JoinedDate"].Value = this.dateTimePicker2.Text;

                        cmd.Parameters.Add("@Class", System.Data.OleDb.OleDbType.VarChar);
                        cmd.Parameters["@Class"].Value = this.textBox5.Text;

                        cmd.Parameters.Add("@Gender", System.Data.OleDb.OleDbType.VarChar);
                        cmd.Parameters["@Gender"].Value = gender;

                        _wait.ShowDialog();

                        System.Media.SoundPlayer _sound = new System.Media.SoundPlayer(@"C:\Windows\Media\Windows Exclamation.wav");
                        _sound.Play();

                        DialogResult _dialogResult = MessageBox.Show("Added Successfully!", "Success", MessageBoxButtons.OK);

                        cmd.ExecuteNonQuery();
                    }

                    conn.Close();
                }
            }
        }

这是图片：

  

button1_Click适用于上传照片（图片将显示在顶部    右上角）

     

button2_Click用于提交（向数据库添加数据）

任何人都可以帮助我？

你的回答非常感谢！

Answer 1

我猜（也许是错的）错误发生在这一行：

fsStream = new FileStream(this.imagePath, FileMode.Open, FileAccess.Read);

所以你应该添加一个空检查

if (this.imagePath != null)

在此行之前，并更正以下代码。

正如您在msdn中看到的，如果路径为空，FileStream的这个ctor将引发ArgumentNullException。