使用C＃在Windows窗体中级联comboBox [英] cascading comboBox in windows form using c#
问题描述
我正在尝试从Windows窗体应用程序中的同一张表更改的combobox1 selectedText上填充Combobox2。我正在使用sql serevr 2008数据库。我无法在combobox中选择的文本更改后填充combobox2。
I am trying to Fill Combobox2 on combobox1 selectedText changed from the same table in windows form application. I am using sql serevr 2008 database. I am unable to fill combobox2 on combobox selected text changed.
这是我尝试过的内容：
private void Purchase_Load(object sender, EventArgs e)
{
fillName();
comboBoxName.SelectedIndex = -1;
}
private void comboBoxName_SelectedIndexChanged(object sender, EventArgs e)
{
if (comboBoxName.SelectedText != "")
{
fillMake();
}
}
private void fillName()
{
SqlConnection con = new SqlConnection(@"Data Source=ashish-pc\;Initial Catalog=HMS;Integrated Security=True");
con.Open();
string str = "Select Item_Name from Item";
SqlCommand cmd = new SqlCommand(str, con);
SqlDataAdapter adp = new SqlDataAdapter(str, con);
DataTable dtItem = new DataTable();
adp.Fill(dtItem);
cmd.ExecuteNonQuery();
comboBoxName.DataSource = dtItem;
comboBoxName.DisplayMember = "Item_Name";
comboBoxName.ValueMember = "Item_Make";
}
private void fillMake()
{
SqlConnection con = new SqlConnection(@"Data Source=ashish-pc\;Initial Catalog=HMS;Integrated Security=True");
con.Open();
string str = "Select Item_Make from Item Where Item_Name='" + comboBoxName.SelectedText + "'";
SqlCommand cmd = new SqlCommand(str, con);
SqlDataAdapter adp = new SqlDataAdapter(str, con);
DataTable dtItem = new DataTable();
adp.Fill(dtItem);
cmd.ExecuteNonQuery();
comboBoxName.DataSource = dtItem;
comboBoxName.DisplayMember = "Item_Make";
comboBoxName.ValueMember = "Item_Name";
comboBoxName.SelectedIndex = -1;
comboBoxName.Text = "Select";
}
项目的Sql服务器表
Item_Code Item_Name Item_Make Item_Price UnitofMeasurement
Cable anchor 45.0000 meter
Cable polycab 30.0000 meter
Button anchor 15.0000 unit
Button havells 20.0000 unit
Switch cona 70.0000 unit
我一直在寻找解决方案，但很不幸。
，请帮帮我。
预先感谢。
I have searched for solution but was unfortunate. please help me out. Thanks in advance.
推荐答案
要弄清楚您要执行的操作有点困难，但是听起来您好像要填充第二个组合框（ comboBoxMake ?？），具体取决于在 comboBoxName 中选择的内容。我以这个假设为基础。抱歉，如果我遇到这个错误。
It's a little difficult to figure out what you're trying to do, but it sounds like you are trying to populate a second combo box (comboBoxMake?) depending on what is selected in comboBoxName. I am basing this answer on that assumption. Apologies if I have this wrong.
这段代码中有很多事情需要注意。我们先来看 fillName（）。
There are lot of things that need attention in this code. Let's look at fillName() first.
private void fillName()
{
SqlConnection con = new SqlConnection(@"Data Source=ashish-pc\;Initial Catalog=HMS;Integrated Security=True");
con.Open();
string str = "Select Item_Name from Item";
SqlCommand cmd = new SqlCommand(str, con);
SqlDataAdapter adp = new SqlDataAdapter(str, con);
DataTable dtItem = new DataTable();
adp.Fill(dtItem);
cmd.ExecuteNonQuery();
comboBoxName.DataSource = dtItem;
comboBoxName.DisplayMember = "Item_Name";
comboBoxName.ValueMember = "Item_Make";
}
您需要 Dispose（）您的数据库对象。可以使用使用{..} 块很干净地完成此操作。
You need to Dispose() your database objects. This can be accomplished pretty cleanly with using { .. } blocks.
您无需手动打开连接;用数据适配器
填充表会自动执行此操作。
You don't need to manually open the connection; filling the table with the data adapter does this automatically.
您不需要调用 ExecuteNonQuery（）。
您应该使用 SqlDataAdapter 带有命令对象的构造函数重载，因为您已经
You should use the SqlDataAdapter constructor overload that takes a command object, since you have already manually created the command.
最后，根据我对目标的假设，我在查询中添加了 distinct 因此它只会获得唯一的 Item_Name s。
Finally, based on my assumption of your goal I have added a distinct to your query so it only gets the unique Item_Names.
private void fillName()
{
string str = "Select distinct Item_Name from Item";
using (SqlConnection con = new SqlConnection(@"Data Source=ashish-pc\;Initial Catalog=HMS;Integrated Security=True"))
{
using (SqlCommand cmd = new SqlCommand(str, con))
{
using (SqlDataAdapter adp = new SqlDataAdapter(cmd))
{
DataTable dtItem = new DataTable();
adp.Fill(dtItem);
comboBoxName.DataSource = dtItem;
comboBoxName.DisplayMember = "Item_Name";
comboBoxName.ValueMember = "Item_Name";
}
}
}
}
到 fillMake（）。我上面已经提到了同样的建议。另外：
On to fillMake(). The same suggestions apply that I noted above. Additionally:
参数化您的SQL。 参数化您的SQL 。这不仅比串联SQL更安全，而且更加干净。认真阅读有关SQL注入的信息： http://en.wikipedia.org/wiki/SQL_injection
Parameterize your SQL. Parameterize your SQL. Not only is this far, far safer than concatenating your SQL together, it is much cleaner. Seriously, read about SQL injection: http://en.wikipedia.org/wiki/SQL_injection
原始帖子中的 fillMake（）方法似乎正在填充 comboBoxName 。这样对吗？您提到了两个组合框，但是您的代码仅引用了一个。我假设您的意思是在此处填充另一个组合框（ comboBoxMake ？）：
The fillMake() method in your original post seems to be repopulating comboBoxName. Is this correct? You mention two combo boxes but your code only references one. I am assuming you mean to populate another combo box (comboBoxMake?) here:
private void fillMake()
{
string str = "Select Item_Make from Item Where Item_Name = @item_name";
using (SqlConnection con = new SqlConnection(@"Data Source=ashish-pc\;Initial Catalog=HMS;Integrated Security=True"))
{
using (SqlCommand cmd = new SqlCommand(str, con))
{
cmd.Parameters.AddWithValue("@item_name", comboBoxName.Text);
using (SqlDataAdapter adp = new SqlDataAdapter(cmd))
{
DataTable dtItem = new DataTable();
adp.Fill(dtItem);
comboBoxMake.DataSource = dtItem;
comboBoxMake.DisplayMember = "Item_Make";
comboBoxMake.ValueMember = "Item_Make";
comboBoxMake.SelectedIndex = -1;
comboBoxMake.Text = "Select";
}
}
}
}
最后，请更改事件处理程序中的代码，以便它查看 Text 而不是 SelectedText 属性：
Lastly, change the code in the event handler so it looks at the Text rather than the SelectedText property:
private void comboBoxName_SelectedIndexChanged(object sender, EventArgs e)
{
if (!string.IsNullOrEmpty(comboBoxName.Text)) // Text instead of SelectedText
{
fillMake();
}
}
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