C# 选定的组合框到文本框
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Selected ComboBox to Text Box
提问by Chris Turner
I am working on creating a form which pulls data from a database, and supplies two combo boxes. ComboBox1 shows Employee name in a "First name Last Name" format. ComboBox2 shows the Employee names in "Last, First" format. The names are pulling into the combo boxes without any difficulty.
我正在创建一个从数据库中提取数据的表单，并提供两个组合框。ComboBox1 以“名字姓氏”格式显示员工姓名。ComboBox2 以“Last, First”格式显示员工姓名。这些名称毫无困难地进入了组合框。
What I am attempting to figure out how to do is once a user selects a name from either of the drop down boxes that it will populate certain text boxes such as, textBox1, textBox2 based on other information from the Query.
我试图弄清楚如何做的是，一旦用户从任一下拉框中选择一个名称，它将根据查询中的其他信息填充某些文本框，例如 textBox1、textBox2。
I have attempted to use
我曾尝试使用
textBox1.Text = comboBox1.SelectedItem;
however, I get an error stating: Cannot implicitly convert type 'object' to 'string'. An explicit conversion exists (are you missing a cast?)
但是，我收到一条错误消息：无法将类型“对象”隐式转换为“字符串”。存在显式转换（您是否缺少演员表？）
Here is my current code. I have left out the connection queries to databases and such intentionally.
这是我当前的代码。我故意省略了对数据库的连接查询等。
public partial class Employees : Form
{
public Employees()
{
InitializeComponent();
//Connect to database for Employees Table Headers
SqlConnection myConnection = new SqlConnection(@"Server=Server...");
try {
myConnection.Open();
string SqlDataPull = String.Format("SELECT * FROM Employees WHERE Lname IS NOT NULL {0} ORDER By Lname", (checkBox1.Checked ? "AND Active='Y'" : ""));
SqlCommand cmd = new SqlCommand(SqlDataPull, myConnection);
cmd.CommandType = CommandType.Text;
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read()) {
string strEmployee = String.Format("{0} {1}", dr["Fname"], dr["Lname"]);
comboBox1.Items.Add(strEmployee);
textBox1.Text = comboBox1.SelectedItem;
string strEmployee2 = String.Format("{0}, {1}", dr["Lname"], dr["Fname"]);
comboBox2.Items.Add(strEmployee2);
}
} catch (Exception e) {
MessageBox.Show(e.ToString());
} finally {
if (myConnection != null) {
myConnection.Dispose();
}
}
}
private void button1_Click(object sender, EventArgs e)
{
Main myNewForm = new Main();
myNewForm.Show();
this.Close();
}
private void button2_Click(object sender, EventArgs e)
{
Reports myNewForm = new Reports();
myNewForm.Show();
this.Close();
}
}
采纳答案by LarsTech
In your SelectedIndexChanged event, add the code:
在 SelectedIndexChanged 事件中，添加代码：
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
if (comboBox1.SelectedIndex == -1) {
textBox1.Text = string.Empty;
} else {
textBox1.Text = comboBox1.SelectedItem.ToString();
}
}
You should probably remove this statement from your while loop:
您可能应该从 while 循环中删除此语句：
// textBox1.Text = comboBox1.SelectedItem;
because you just added the item to the ComboBox items collection, but you don't actually know it's been selected.
因为您刚刚将该项目添加到 ComboBox 项目集合中，但您实际上并不知道它已被选中。
Also, make sure you wire the event up:
另外，请确保将事件连接起来：
public Employees()
{
InitializeComponent();
// yada-yada-yada
comboBox1.SelectedIndexChanged += comboBox1_SelectedIndexChanged;
}
回答by Spacemancraig
What you need is to use the TEXT value so instead of textBox1.Text = comboBox1.SelectedItem;It should be textBox1.Text = comboBox1.SelectedItem.ToString();or simply textBox1.Text = comboBox1.Text
您需要的是使用 TEXT 值，而不是textBox1.Text = comboBox1.SelectedItem;It should betextBox1.Text = comboBox1.SelectedItem.ToString();或简单地textBox1.Text = comboBox1.Text
回答by Jaime Torres
If all you need is the text, you can simply use:
如果您只需要文本，则可以简单地使用：
textBox1.Text = comboBox1.Text;
回答by dtsg
You need to use:
您需要使用：
textBox1.Text = comboBox1.SelectedItem.Textto get the text part of the item.
textBox1.Text = comboBox1.SelectedItem.Text获取项目的文本部分。
SelectedItemis an object and you're trying to assign it to the Textproperty of the text box.
SelectedItem是一个对象，您正试图将其分配给Text文本框的属性。
回答by Olivier Jacot-Descombes
Since you can fill a ComboBoxwith items of any type (not just string) the SelectedItemproperty has a type of object. If you inserted stringsyou can retrieve them by casting
由于您可以ComboBox使用任何类型（不仅仅是string）的项目填充 a ，因此该SelectedItem属性的类型为object。如果您插入，strings您可以通过投射来检索它们
string s = (string)myComboBox.SelectedItem;
If you added items of some other type like a class Person, you can either retrieve this object or get its string or some property with
如果添加了其他类型的项目，如类Person，则可以检索此对象或获取其字符串或某些属性
Person p = (Person)myComboBox.SelectedItem;
string s = myComboBox.SelectedItem.ToString();
string lastName = ((Person)myComboBox.SelectedItem).LastName;
回答by Josko
Unfortunatly you can't do this:
不幸的是，你不能这样做：
textBox1.Text = comboBox1.SelectedItem.ToString();
because the result is also path:
因为结果也是路径：
System.Windows.Controls.ComboBoxItem: Citroen
You need only value for example Citroen
您只需要价值，例如雪铁龙
So problem can be resolved by searching for string like this:
所以问题可以通过搜索这样的字符串来解决：
string auto = comboBox1.SelectedItem.ToString();
int index = auto.IndexOf(" ");
carModel.Text = auto.Substring(index+1);
