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我是 Windows 窗体和 SQL Server 的初学者，所以请原谅我糟糕的代码。我正在尝试根据表单上的字段更新我的 SQL 服务器上的数据。这是表格，

在此处输入图像描述

这是选择图像按钮单击事件代码，

String imgLocation = "";
private void btnInvChooseImg_Click(object sender, EventArgs e)
    {
        try
        {
                OpenFileDialog openFileDialog = new OpenFileDialog();
                openFileDialog.Filter = "JPG Files (*.jpg)|*.jpg|PNG Files (*.png)|.png|All Files (*.*)|*.*";
                openFileDialog.Title = "Select Product Image";

                if (openFileDialog.ShowDialog() == DialogResult.OK)
                {
                    imgLocation = openFileDialog.FileName.ToString();
                    pbInvImg.ImageLocation = imgLocation;
                }               

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }

这是更新按钮点击事件代码，

private void btnUpdate_Click(object sender, EventArgs e)
    {
        con.Open();
        try
        {
            if (txtProdName.Text != "" && txtProdDesc.Text != "" && txtQuantity.Text != "" && cmbAddCategory.Text != "" && pbInvImg.Image != null)
            {
                byte[] img = null;
                FileStream fileStream = new FileStream(imgLocation, FileMode.Open, FileAccess.Read);
                BinaryReader binaryReader = new BinaryReader(fileStream);
                img = binaryReader.ReadBytes((int)fileStream.Length);
                cmd = new SqlCommand(@"UPDATE PRODUCTS 
                                            SET ProductImage = @img, 
                                                ProductName = '" + txtProdName.Text
                                                        + "', ProductDescription = '" + txtProdDesc.Text
                                                        + "', Quantity = '" + txtQuantity.Text
                                                        + "', CID = (SELECT CID FROM CATEGORY WHERE CategoryName = '" + cmbAddCategory.Text
                                                        + "') WHERE PID = '" + lblProdID.Text + "';", con);
                cmd.Parameters.Add(new SqlParameter("@img", img));
                cmd.ExecuteNonQuery();
                con.Close();
                MessageBox.Show("Product updated successfully.");
                loadInventory();
                clearFields();

            }
            else if (txtProdName.Text == "" || txtProdDesc.Text == "" || txtQuantity.Text == "" || cmbAddCategory.Text == "" || pbInvImg.Image == null)
            {
                MessageBox.Show("Please supply all fields.");
            }

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message, Application.ProductName, MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }

如果我选择不同的图像，更新工作正常，但如果我只想更新/更改产品名称而不是图像，则会出现错误，提示错误路径名称不合法。知道我错过了什么吗？谢谢你。

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1 回答 1

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你试过调试吗？它将帮助您了解错误发生的位置。

很可能是因为 imgLocation 像@Wouter 提到的那样为空。您应该在调用之前检查 imgLocation FileStream fileStream = new FileStream(imgLocation, FileMode.Open, FileAccess.Read);。这可能是错误的地方。

if (File.Exists(imgLocation)) {
    FileStream fileStream = new FileStream(imgLocation, FileMode.Open, FileAccess.Read);
    BinaryReader binaryReader = new BinaryReader(fileStream);
    img = binaryReader.ReadBytes((int)fileStream.Length);
}
else {
    # Tell them to choose a valid image or implement your own logic for what should happen.
    Message.Box($"The image at {imgLocation} doesn't exist. Please choose a valid image");
}

并参数化您的输入。请。

于 2020-06-10T16:43:52.940 回答