一直停留在从数据库中读取数据
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【中文标题】一直停留在从数据库中读取数据【英文标题】：Keep stuck at the reading the data from database 【发布时间】：2013-08-30 10:04:05 【问题描述】：我想用我在运行程序时给出的值减去数据库中的数据。一切正常，但我一直停留在newVal。我已经这样做了，但是newValkeep出现0（因为我声明了decimal newVal = 0，但是在这个问题上，我只是使用了decimal newVal;）。还有两个问题：如果我将newVal = ... 移到顶部，它是没用的，因为newVal 中的计算之一是从数据库中读取数据（因为我希望数据库减去我运行时给出的新值程序，需要dReader = cmd.ExecuteReader();），但是如果我在读取数据后将newVal放在底部，那也没用，因为我设置了Quantity = ?，而?的值是newVal..嗯，这里是代码：
private void AddObjects(object sender, EventArgs e, Form theForm)
button1.Visible = true;
textBoxQuantityContainer = new List<NumericUpDown>();
textBoxCodeContainer = new List<NumericTextBox>();
textBoxDescContainer = new List<TextBox>();
textBoxSubTotalContainer = new List<TextBox>();
textBoxTotalContainer = new List<TextBox>();
textBoxAllTotalContainer = new TextBox();
OleDbDataReader dReader;
OleDbConnection conn = new OleDbConnection(connectionString);
conn.Open();
OleDbCommand cmd = new OleDbCommand("SELECT [Code] FROM [Seranne]", conn);
dReader = cmd.ExecuteReader();
AutoCompleteStringCollection codesCollection = new AutoCompleteStringCollection();
while (dReader.Read())
string numString = dReader[0].ToString().PadLeft(4, '0');
codesCollection.Add(numString);
dReader.Close();
conn.Close();
if (firstForm.comboBox1.SelectedIndex == 0)
label1.Text = "Code:";
label1.Location = new Point(60, 125);
label2.Text = "Welcome to the Selling System.";
label2.Location = new Point(600, 30);
label3.Text = "Quantity:";
label3.Location = new Point(155, 125);
label4.Text = "Description:";
label4.Location = new Point(580, 125);
label5.Text = "Sub Total on Rp:";
label5.Location = new Point(1020, 125);
label6.Text = "Total on Rp:";
label6.Location = new Point(1210, 125);
label7.Text = "Total on Rp:";
label7.Location = new Point(1080, 580);
else if (firstForm.comboBox1.SelectedIndex == 1)
label1.Text = "Kode:";
label1.Location = new Point(60, 125);
label2.Text = "Selamat datang di Selling System.";
label2.Location = new Point(600, 30);
label3.Text = "Banyaknya:";
label3.Location = new Point(145, 125);
label4.Text = "Keterangan:";
label4.Location = new Point(580, 125);
label5.Text = "Sub Total di Rp:";
label5.Location = new Point(1020, 125);
label6.Text = "Total di Rp:";
label6.Location = new Point(1210, 125);
label7.Text = "Total di Rp:";
label7.Location = new Point(1080, 580);
//****TextBox for Code****
for (int y = 0; y <= 16; y++)
textBoxCodeContainer.Add(new NumericTextBox());
textBoxCodeContainer[y].Size = new Size(100, 50);
textBoxCodeContainer[y].Location = new Point(25, 150 + (y * 25));
textBoxCodeContainer[y].TextChanged += new System.EventHandler(this.textBox_TextChanged);
textBoxCodeContainer[y].AutoCompleteMode = AutoCompleteMode.Suggest;
textBoxCodeContainer[y].AutoCompleteSource = AutoCompleteSource.CustomSource;
textBoxCodeContainer[y].AutoCompleteCustomSource = codesCollection;
theForm.Controls.Add(textBoxCodeContainer[y]);
//****TextBox for Quantity****
for (int y = 0; y <= 16; y++)
textBoxQuantityContainer.Add(new NumericUpDown());
textBoxQuantityContainer[y].Size = new Size(100, 50);
textBoxQuantityContainer[y].Location = new Point(125, 150 + (y * 25));
textBoxQuantityContainer[y].TextChanged += new System.EventHandler(this.textBox_TextChanged);
textBoxQuantityContainer[y].Maximum = 1000;
theForm.Controls.Add(textBoxQuantityContainer[y]);
//****TextBox for Description****
for (int y = 0; y <= 16; y++)
textBoxDescContainer.Add(new TextBox());
textBoxDescContainer[y].Size = new Size(750, 50);
textBoxDescContainer[y].Location = new Point(225, 150 + (y * 25));
theForm.Controls.Add(textBoxDescContainer[y]);
//****TextBox for Sub Total****
for (int y = 0; y <= 16; y++)
textBoxSubTotalContainer.Add(new TextBox());
textBoxSubTotalContainer[y].Size = new Size(175, 50);
textBoxSubTotalContainer[y].Location = new Point(975, 150 + (y * 25));
theForm.Controls.Add(textBoxSubTotalContainer[y]);
//****TextBox for Total****
for (int y = 0; y <= 16; y++)
textBoxTotalContainer.Add(new TextBox());
textBoxTotalContainer[y].Size = new Size(175, 50);
textBoxTotalContainer[y].Location = new Point(1150, 150 + (y * 25));
textBoxTotalContainer[y].TextChanged += new System.EventHandler(this.textBox_TextChanged);
theForm.Controls.Add(textBoxTotalContainer[y]);
//****TextBox for Total All****
textBoxAllTotalContainer.Size = new Size(175, 50);
textBoxAllTotalContainer.Location = new Point(1150, 575);
textBoxAllTotalContainer.TextChanged += new System.EventHandler(this.textBox_TextChanged);
theForm.Controls.Add(textBoxAllTotalContainer);
private void UpdateDatas()
int codeValue = 0;
int index = 0;
string query = "SELECT [Quantity], [Description], [Price] FROM [Seranne] WHERE [Code] IN (";
OleDbConnection conn = new OleDbConnection(connectionString);
conn.Open();
if (int.TryParse(this.textBoxCodeContainer[0].Text, out codeValue))
query = query + codeValue.ToString();
for (int i = 1; i < 17; i++)
if (int.TryParse(this.textBoxCodeContainer[i].Text, out codeValue))
query = query + "," + codeValue.ToString();
query = query + ")";
OleDbCommand cmd = new OleDbCommand(query, conn);
OleDbDataReader dReader;
dReader = cmd.ExecuteReader();
while (dReader.Read())
if (textBoxCodeContainer[index].TextLength != 0)
this.textBoxQuantityContainer[index].Maximum = Convert.ToInt32(dReader["Quantity"].ToString());
this.textBoxDescContainer[index].Text = dReader["Description"].ToString();
this.textBoxSubTotalContainer[index].Text = dReader["Price"].ToString();
index += 1;
dReader.Close();
conn.Close();
private void UpdatePrice()
int totalPrice = 0;
int quantity = 0;
int price = 0;
for (int i = 0; i < 17; i++)
if (textBoxQuantityContainer[i].Value > 0)
quantity = (int)textBoxQuantityContainer[i].Value;
price = Convert.ToInt32(textBoxSubTotalContainer[i].Text);
textBoxTotalContainer[i].Text = (quantity * price).ToString();
else
textBoxSubTotalContainer[i].Text = "";
textBoxTotalContainer[i].Text = "";
for (int i = 0; i < 17; i++)
if (textBoxTotalContainer[i].TextLength != 0)
totalPrice += Convert.ToInt32(textBoxTotalContainer[i].Text);
textBoxAllTotalContainer.Text = totalPrice.ToString("n2");
private void UpdateQuantity()
int index = 0;
int codeValue = 0;
decimal newVal;
List<int> integers = new List<int>();
foreach (var tb in textBoxCodeContainer)
if (int.TryParse(tb.Text, out codeValue))
integers.Add(codeValue);
string command = "UPDATE [Seranne] SET [Quantity]=? WHERE [Code] IN(" + string.Join(", ", integers) + ")";
OleDbConnection conn = new OleDbConnection(connectionString);
OleDbCommand cmd = new OleDbCommand(command, conn);
cmd.Parameters.Add("Quantity", System.Data.OleDb.OleDbType.Integer);
cmd.Parameters["Quantity"].Value = this.newVal.ToString();
OleDbDataReader dReader;
conn.Open();
dReader = cmd.ExecuteReader();
while (dReader.Read())
if (textBoxQuantityContainer[index].Value != 0)
newVal = (Convert.ToInt32(dReader["Quantity"].ToString()) -
textBoxQuantityContainer[index].Value);
int numberOfRows = cmd.ExecuteNonQuery();
index += 1;
if (newVal == 0)
System.Media.SoundPlayer sounds = new System.Media.SoundPlayer(@"C:\Windows\Media\Windows Notify.wav");
sounds.Play();
MessageBox.Show("Cannot Update", "Error");
else
System.Media.SoundPlayer sound = new System.Media.SoundPlayer(@"C:\Windows\Media\Windows Notify.wav");
sound.Play();
MessageBox.Show("Was Updated Successfully", "Success");
dReader.Close();
conn.Close();
private void textBox_TextChanged(object sender, EventArgs e)
UpdateDatas();
UpdatePrice();
private void button1_Click(object sender, EventArgs e)
UpdateQuantity();
非常感谢
【问题讨论】：
你能告诉我你为什么比较这些领域吗？textBoxQuantityContainer[index].Value >= Convert.ToInt32(dReader["Quantity"].ToString()数量只能增长？
嗨@JeroenvanLangen：你问的问题已经被我回答了，在你的回答中。谢谢
【参考方案1】：
美好的一天，我在这里得到了一些东西：
1) 这里不需要cmd.Parameters["Quantity"].Value = this.newVal.ToString(); 转换为字符串，因为Value 是一个对象。您已经定义了它应该作为整数处理。
2) 将查询中的? 替换为@Quantity，这样它将被查询执行填充。
3) 更新时，您不需要以阅读器的身份执行它。使用不带循环的int numberOfRows = cmd.ExecuteNonQuery();。它将更新所有项目。
4) 您应该在构建整数列表时执行if (textBoxQuantityContainer[index].Value != 0 && textBoxQuantityContainer[index].Value >=
Convert.ToInt32(dReader["Quantity"].ToString()))
，这样您只会更新正确的数量。
如果您只想更新某些行，则必须扩展 where 子句：
cmd.Parameters.Add("MinimumQuantity", System.Data.OleDb.OleDbType.Integer).Value = minimumQuantity;
string command = "UPDATE [Seranne]
SET [Quantity]=@Quantity
WHERE [Code] IN(" + string.Join(", ", integers) + ")
AND [Quantity] > @MinimumQuantity
最大的风险是：您假设您的 textBoxCodeContainer 和数据库之间的记录顺序和数量相同。
文本框和行之间的关系是什么。你怎么知道哪个文本框链接到哪一行？
如果您向我展示更多代码（例如 textBoxCodeContainer 的定义位置/方式），我可以向您推动正确的方向
更新：
我编写了一些代码来读取和操作您的数据库，这是未测试的，因为我这里没有任何数据库。
我会创建这些类，1 是数据类 Product，1 是 Handler 类 ProductHandler。
数据类只包含数据（不是表示格式）数据处理程序知道如何读取和写入它们。
public class Product
public int Code get; set;
public string Description get; set;
public int Quantity get; set;
public class ProductHandler
public ProductHandler(string connectionString)
ConnectionString = connectionString;
public bool AddProduct(Product product)
return AddProducts(new Product[] product ) > 0;
public int AddProducts(IEnumerable<Product> products)
int rowsInserted = 0;
using (OleDbConnection conn = new OleDbConnection(ConnectionString))
conn.Open();
string query = "INSERT INTO [Seranne] (Code, Description, Quantity) VALUES(@Code, @Description, @Quantity)";
using (OleDbCommand cmd = new OleDbCommand(query, conn))
cmd.Parameters.Add("Code", OleDbType.Integer);
cmd.Parameters.Add("Description", OleDbType.VarChar);
cmd.Parameters.Add("Quantity", OleDbType.Integer);
foreach (var product in products)
cmd.Parameters["Code"].Value = product.Code;
cmd.Parameters["Description"].Value = product.Description;
cmd.Parameters["Quantity"].Value = product.Quantity;
rowsInserted += cmd.ExecuteNonQuery();
return rowsInserted;
public bool UpdateProduct(Product product)
return UpdateProducts(new Product[] product ) > 0;
public int UpdateProducts(IEnumerable<Product> products)
int rowsUpdated = 0;
using (OleDbConnection conn = new OleDbConnection(ConnectionString))
conn.Open();
string query = "UPDATE [Seranne] SET Description = @Description, Quantity = @Quantity WHERE [Code] == @Code)";
using (OleDbCommand cmd = new OleDbCommand(query, conn))
cmd.Parameters.Add("Code", OleDbType.Integer);
cmd.Parameters.Add("Description", OleDbType.VarChar);
cmd.Parameters.Add("Quantity", OleDbType.Integer);
foreach (var product in products)
cmd.Parameters["Code"].Value = product.Code;
cmd.Parameters["Description"].Value = product.Description;
cmd.Parameters["Quantity"].Value = product.Quantity;
rowsUpdated += cmd.ExecuteNonQuery();
return rowsUpdated;
public bool DeleteProduct(Product product)
return DeleteProducts(new int[] productCode ) > 0;
public int DeleteProducts(IEnumerable<Product> products)
using (OleDbConnection conn = new OleDbConnection(ConnectionString))
conn.Open();
string productCodeStr = string.Join(", ", products.Select(item => item.Code));
string query = string.Format("DELETE FROM [Seranne] WHERE [Code] in (0)", productCodeStr);
using (OleDbCommand cmd = new OleDbCommand(query, conn))
int rowsDeleted = cmd.ExecuteNonQuery();
return rowsDeleted;
public IEnumerable<Product> ReadAllProducts()
List<Product> result = new List<Product>();
using (OleDbConnection conn = new OleDbConnection(ConnectionString))
conn.Open();
using (OleDbCommand cmd = new OleDbCommand("SELECT [Code], [Description], [Quantity] FROM [Seranne]", conn))
using (OleDbDataReader dReader = cmd.ExecuteReader())
while (dReader.Read())
Product product = new Product();
product.Code = Convert.ToInt32(dReader["Code"]);
product.Description = Convert.ToString(dReader["Description"]);
product.Quantity = Convert.ToInt32(dReader["Quantity"]);
result.Add(product);
return result;
public string ConnectionString get; private set;
一些示例代码：
ProductHandler _productHandler = new ProductHandler("connectionstring here or from config");
public void Example()
_productList.Clear();
_productList.AddRange(_productHandler.ReadAllProducts());
// displaying
foreach (var product in _productList)
Trace.WriteLine(string.Format("code: 0, description: 1, quantity: 2", product.Code, product.Description, product.Quantity);
// updating
var selectedProduct = _productList.FirstOrDefault(item => item.Code == 15);
if(selectedProduct!= null)
selectedProduct.Quantity = 50;
_productHandler.UpdateProduct(selectedProduct);
// deleting
_productHandler.DeleteProducts(_productList.Where(item => item.Quantity < 5));
如何将文本框链接到正确的产品：
我将创建一个包含 Product 属性和 TextBoxes 的 UserControl，并在 textbox_changed 事件发生时处理。这些事件处理程序操纵 Product 实例。
您只生成 16 个控件并将产品绑定到它。当您按下一个按钮时，您只需要保存更改的产品即可。
【讨论】：
我仍然不明白你为什么在那里做 If 语句，为什么数量要大于存储的数量？ 嗨@Jeroen van Langen，感谢您回答我的问题。系统会在用户输入Product Code时识别出来，Product Code是用户必须做的第一件事，为了显示包括价格在内的所有数据，它指的是哪个Product Code。所以，所有的数据和价格都是根据Product Code显示的，我再给你看一些代码，请再次参考问题。谢谢而且，我不明白你在第 4 位的回答中是什么意思。
我在知道textBoxQuantityContainer 的值可以设置为最大值之前就这样做了。忽略它。而且我已经知道我可以设置最大值，所以只知道我删除了“数量大于存储数量”的语句。谢谢
我建议将数据和表示按繁忙对象分开。现在您正在引用 sql 更新方法中的控件。如果你愿意，我可以给你一个例子。这也将使人们更容易理解正在发生的事情。
当然，这样会更好。因为，我不知道如何解决这个问题。以上是关于一直停留在从数据库中读取数据的主要内容，如果未能解决你的问题，请参考以下文章