[英]Combobox not showing Items while selecting the parameter from Listbox c#
我希望每次我从 ListBox 中选择某些内容时,我的 ComboBox 都显示一组参数,但它没有在 ComboBox 中显示任何内容。
这是我到目前为止...
private void Form1_Load(object sender, EventArgs e)
{
listBox4.Items.Add("BE");
listBox4.Items.Add("MBA");
listBox4.Items.Add("Pharmacy");
}
private void listBox4_SelectedIndexChanged(object sender, EventArgs e)
{
}
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
if ((string)listBox4.SelectedItem == "BE")
{
comboBox1.Items.Add("CSE");
comboBox1.Items.Add("IT");
comboBox1.Items.Add("ME");
comboBox1.Items.Add("EX");
comboBox1.Items.Add("CE");
}
if ((string)listBox4.SelectedItem == "Pharmacy")
{
comboBox1.Items.Add("Pharmaceutical Chemistry");
comboBox1.Items.Add("Pharmacology");
}
if ((string)listBox4.SelectedItem == "MBA")
{
comboBox1.Items.Add("Retail Management");
comboBox1.Items.Add("HR");
}
}
这是输出
您将代码放在错误的事件中。
// This is where your code belongs.
private void listBox4_SelectedIndexChanged(object sender, EventArgs e)
{
if ((string)listBox4.SelectedItem == "BE")
{
comboBox1.Items.Add("CSE");
comboBox1.Items.Add("IT");
comboBox1.Items.Add("ME");
comboBox1.Items.Add("EX");
comboBox1.Items.Add("CE");
}
if ((string)listBox4.SelectedItem == "Pharmacy")
{
comboBox1.Items.Add("Pharmaceutical Chemistry");
comboBox1.Items.Add("Pharmacology");
}
if ((string)listBox4.SelectedItem == "MBA")
{
comboBox1.Items.Add("Retail Management");
comboBox1.Items.Add("HR");
}
}
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
// THIS WAS THE WRONG PLACE
}
您应该为控件指定有意义的名称,以便更容易确定来自何处的内容。
每当填充 ComboBox 时,您应该先清除它。
最重要的是,您正在检查 ComboBox 而不是 ListBox 上的SelectedIndexChanged
。 如果向上移动会发生什么?
private void Form1_Load(object sender, EventArgs e)
{
listBox4.Items.Add("BE");
listBox4.Items.Add("MBA");
listBox4.Items.Add("Pharmacy");
}
private void listBox4_SelectedIndexChanged(object sender, EventArgs e)
{
if ((string)listBox4.SelectedItem == "BE")
{
comboBox1.Items.Add("CSE");
comboBox1.Items.Add("IT");
comboBox1.Items.Add("ME");
comboBox1.Items.Add("EX");
comboBox1.Items.Add("CE");
}
if ((string)listBox4.SelectedItem == "Pharmacy")
{
comboBox1.Items.Add("Pharmaceutical Chemistry");
comboBox1.Items.Add("Pharmacology");
}
if ((string)listBox4.SelectedItem == "MBA")
{
comboBox1.Items.Add("Retail Management");
comboBox1.Items.Add("HR");
}
}
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
}
private void Form1_Load(object sender, EventArgs e)
{
listBox4.Items.Add("BE");
listBox4.Items.Add("MBA");
listBox4.Items.Add("Pharmacy");
}
private void listBox4_SelectedIndexChanged(object sender, EventArgs e)
{
comboBox1.Items.Clear();
if ((string)listBox4.SelectedItem == "BE")
{
comboBox1.Items.Add("CSE");
comboBox1.Items.Add("IT");
comboBox1.Items.Add("ME");
comboBox1.Items.Add("EX");
comboBox1.Items.Add("CE");
}
if ((string)listBox4.SelectedItem == "Pharmacy")
{
comboBox1.Items.Add("Pharmaceutical Chemistry");
comboBox1.Items.Add("Pharmacology");
}
if ((string)listBox4.SelectedItem == "MBA")
{
comboBox1.Items.Add("Retail Management");
comboBox1.Items.Add("HR");
}
}
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
}
好吧,您应该更新(删除旧的并添加新的) comboBox1.Items
上的listBox4
更改:
// Please, notice "listBox4"
private void listBox4_SelectedIndexChanged(object sender, EventArgs e) {
String selected = listBox4.SelectedItem as String;
// we don't want blinking - too many re-draws
combobox1.BeginUpdate();
try {
//DONE: do not forget to remove old items
combobox1.Items.Clear();
if (selected == "BE") {
combobox1.Items.AddRange("CSE", "IT", "ME", "EX", "CE");
else if (selected == "Pharmacy") {
combobox1.Items.AddRange("Pharmaceutical Chemistry", "Pharmacology");
else if (selected == "MBA")
combobox1.Items.AddRange("Retail Management", "HR");
finally {
combobox1.EndUpdate();
}
}
而且似乎comboBox1
没有用,至少现在是:
private void comboBox1_SelectedIndexChanged(object sender, EventArgs e) {
//TODO: put here logic on comboBox1 change, e.g. on "Retail Management" selection
}
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