C# Empty path name is not legal - Winform

Question

Below this code is my Add button on my windows form. When i tried to click it without adding any image & without path also, error occur that i mentioned below these code. I want to fix this exception, even if the user doesn't add image or file path it doesn't get exception. I know its been asked many times but their exception in their code is different so i'm a bit confused there. Thank you

private void btn_add_Click(object sender, EventArgs e)
    {
        byte[] image = null;
        var stream = new FileStream(this.txt_path.Text, FileMode.Open, FileAccess.Read);
        var read = new BinaryReader(stream);
        image = read.ReadBytes((int)stream.Length);


        using (var con = SQLConnection.GetConnection())
        {


            if (string.IsNullOrEmpty(cbox_supplier.Text) || string.IsNullOrEmpty(txt_code.Text) || string.IsNullOrEmpty(txt_item.Text) || string.IsNullOrEmpty(txt_quantity.Text) || string.IsNullOrEmpty(txt_cost.Text) || string.IsNullOrEmpty(txt_path.Text))
            {
                MetroMessageBox.Show(this, "Please input the Required Fields", "System Message:", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
            }
            else
            {

                var selectCommand = new SqlCommand("Insert into employee_product (Image, Supplier, Codeitem, Itemdescription, Date, Quantity, Unitcost) Values (@Image, @Supplier, @Codeitem, @Itemdescription, @Date, @Quantity, @Unitcost)",con);
                selectCommand.Parameters.AddWithValue("@Image", image);
                selectCommand.Parameters.AddWithValue("@Supplier", cbox_supplier.Text);
                selectCommand.Parameters.AddWithValue("@Codeitem", txt_code.Text.Trim());
                selectCommand.Parameters.AddWithValue("@Itemdescription", txt_item.Text.Trim());
                selectCommand.Parameters.AddWithValue("@Date", txt_date.Text.Trim());
                selectCommand.Parameters.AddWithValue("@Quantity", txt_quantity.Text.Trim());
                selectCommand.Parameters.AddWithValue("@Unitcost", txt_cost.Text.Trim());
                selectCommand.ExecuteNonQuery();
                MessageBox.Show("Added successfully", "SIMS", MessageBoxButtons.OK, MessageBoxIcon.Information, MessageBoxDefaultButton.Button1);
                txt_path.Clear();
                pictureBox1.Image = null;
                txt_code.Clear();
                txt_item.Clear();
                txt_quantity.Clear();
                txt_cost.Clear();
                _view.AddingProduct();

            }

        }
    }
   private void btn_upload_Click(object sender, EventArgs e)
    {
        OpenFileDialog opnfd = new OpenFileDialog();
        opnfd.Filter = "Image Files (*.jpg;*.jpeg;.*.gif;*.png;)|*.jpg;*.jpeg;.*.png;*.gif";
        opnfd.Title = "Select Item";

        if (opnfd.ShowDialog() == DialogResult.OK)
        {
            var path = opnfd.FileName.ToString();
            txt_path.Text = path;
            pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
            pictureBox1.Image = Image.FromFile(opnfd.FileName);

        }
    }

// This is where System Argument Exception occur

        byte[] image = null;
 -----> var stream = new FileStream(this.txt_path.Text, FileMode.Open, FileAccess.Read);
        var read = new BinaryReader(stream);
        image = read.ReadBytes((int)stream.Length);

Answer 1

You can either pre-check the file exists:

if (File.Exists(txt_path.Text))
{
    var stream = new FileStream(this.txt_path.Text, FileMode.Open, FileAccess.Read);
    var read = new BinaryReader(stream);
    image = read.ReadBytes((int)stream.Length);
    // The rest of your code
}

or catch the error when it occurs:

try
{
    var stream = new FileStream(this.txt_path.Text, FileMode.Open, FileAccess.Read);
    var read = new BinaryReader(stream);
    image = read.ReadBytes((int)stream.Length);
    // The rest of your code
}
catch
{
    // Creating filestream object failed.
}

As you asked about wrapping the FileStream in a using statement:

When you open a FileStream you need to explicitly close it and make sure you've disposed of it to remove the open file handle - so that other applications can access the file. You can either do this by calling Close and Dispose or you can just wrap the object in a using statement that will automatically call close and dispose for you.

using (var stream = new FileStream(this.txt_path.Text, FileMode.Open, FileAccess.Read))
{
    using (var read = new BinaryReader(stream))
    {
        image = read.ReadByres((int)stream.Length);
    } // BinaryReader is Closed and Disposed here
} // FileStream is Closed and Disposed here

The FileStream and BinaryReader objects (stream and read) only exist up to the point where the using statements closing brace } is.