I have a list box with my desired information inside it. However I need a number to be sent when the user selects on a specific row.
ListBox data:
Test1
Test2
Test3
For example when I select Test1 in my list my I need to return the integer 2. I am asking if there is anyway I can assign the number 2 to be associated with "Test2"
listbox.Items.Add("Name displayed on list", value);
Yes, ListBox Items are of type object and you can assign any object to them, so build a class like this:
public class ListItem
{
public string Name {get; set;}
public int Value {get; set;}
public override string ToString()
{
return Name;
}
}
Now you can add ListBox Items like this:
listbox.Items.Add(new ListItem { Name = "Test1", Value = 2});
When a ListBox Item is Selected you can get its value like:
var value = ((ListItem)listbox.SelectedItem).Value;
Note that as ListBox Uses its Items .ToString() method to create Texts to show so you have to override it's ToString() method like this:
public override string ToString()
{
return Name;
}
Otherwise it will show the name of the class instead of your desired value.
As already suggested, you could specify DataSource of your listBox, then you could use conviniently SelectedValue of ListBox class. But before you have to also specify ValueMember and DisplayMember of a list box.
The most convinient in my opinion will be adding Tuple<string, int> objects to your list box and settings ValueMember to "Item2" and DisplayMember to "Item1", as Item1 willb e our string Test1 and Item2 will be integer value.
Code example:
listBox1.ValueMember = "Item2";
listBox1.DisplayMember = "Item1";
listBox1.DataSource = new Tuple<string, int>[] {
new Tuple<string, int>("Test1", 1),
new Tuple<string, int>("Test2", 2)
};
Now, in code you can just use listBox1.SelectedValue to access integer value of selected item.
Related
I have many class to set ComboBox datasource
- Position [DISPLAY, VALUE, ID, NAME]
- Division [DISPLAY, VALUE, ID, NAME]
- SubDivision [DISPLAY, VALUE, ID, NAME, DIVISIONID]
- ect.
and i binding data
List<Position> list = new List<Position>;
list.Add(...);
cboPosision.DataSource = list;
How to create method for ComboBox to insert row Null data
private void SetDataSource(this ComboBox cbo, object dataList, bool IncludeAll)
{
if(includeAll) { dataList.Add(null); } //Need Insert object {DISPLAY:"All", VALUE:null}
cbo.DataSource = dataList;
}
Here is one way to do it:
Create a common interface that all your combobox items must implement:
interface IComboBoxItem
{
string Display {get;set;}
object Value {get;set;
}
Then use a generic extension method to set that list as a data source:
private void SetDataSource<T>(this ComboBox cbo, IList<T> dataList, bool IncludeAll) where T : new, IComboBoxItem
{
if(includeAll)
{
dataList.Add(new T() {Display = "All", Value = null});
}
cbo.DisplayMember = "Display"; // This corresponds to the display member of the data object
cbo.ValueMember = "Value"; // this corresponds to the value member of the data object
cbo.DataSource = dataList;
}
Note: code written directly here, there might be some typos.
I already have seen that there are many Topics about this,but I am not able to make them work.
I have an Combobox which shall be filled with an List of String.
this.elementBox.DataSource = this.elementList;
this.elementBox.SelectedIndexChanged += new EventHandler(this.elementBox_SelectedIndexChanged);
If I put this into the Code my GUI does not appear, I suppose the assignment of the data is wrong. I already tried Bindingsource.
Then I want to fill an Combobox with an List of Objects and this does not work either. itemData is an Dictionary with an String as key and the Objectlist as value.
box1.DataSource = itemData["ele1"];
box1.DisplayMember = "Name";
box2.DataSource = itemData["ele2"];
box2.DisplayMember = "Id";
I tried to play around with DisplayMember and Value but I am not able to get it to work.
The Type of the List is MyItem:
class myItem{ int Id; Internal data;}
class Internal {String name;}
Obviously I want to show the myItem.data.name in the Combobox, but I do not know how to get it. Furthermore what is the difference of DisplayMember and Value?
DisplayMember expects a public property not a private field
Change the classes:
class myItem
{
public int Id {get; set}
public Internal data {get;set;}
}
class Internal
{
public string Name {get; set;}
}
Note also that the property names are case sensitive. So 'name' and 'Name' are considered to be different entities.
Further, if you are adding an object of 'myItem` class, you cannot get the combo box to access the a member of a member. You will have to do the fetching yourself:
class myItem
{
public int Id {get; set}
public Internal data {get;set;}
public string Name { get { return data.Name; }}
}
Now by setting DisplayMember to "Name" it will reference the Name property of myItem which in turn accesses the data.Name property.
If the list comes to you from somewhere else (you don't own the list class and thus cannot modify it's code), you will have to wrap the objects inside another class and replace the list with a list of the wrapped objects:
class myItemWrapper
{
private myItem _myItem;
public myItemWrapper(myItem item)
{
_myItem = item;
}
public override string ToString()
{
return _myItem.data.Name;
}
public myItem Item { get { return _myItem;}}
}
then you can get rid of the DisplayMember assignment
box1.DisplayMember = "Name";
as the ToString() will be called instead.
but you have to replace the
box1.DataSource = itemData["ele1"];
with a bit more code:
var wrapper = new List<myItemWrapper>();
foreach(var item in itemData["ele1"]);
wrapper.Add(new myItemWrapper(item));
box1.DataSource = wrapper;
And don't forget that, when you are handling the selected item in the listbox that you are no longer dealing with myItem objects, but myItemWrapper objects instead. So to access the actual myItem object you will have to use the Item property of the myItemWrapper class instead.
I am setting a combobox item like this:
List<Object> items = new List<Object>();
items.Add(new { Text = "MyVal", Value = 1 });
cbo.DataSource = items;
It then in VS returns:
But I cannot simply now say cbo.SelectedItem.Text or cbo.SelectedItem.Value.
If i try this, I get the error
"object does not contain a definition for value and no extension method value
accepting a first argument of type object could be found"
How can I get the Value Property please
Based on great replies, I have now added this, to show that I cannot get the properties of Text or Value at all.
I've tried this code to pass the "string" into
public class ComboboxItem
{
public string Text { get; set; }
public short Value { get; set; }
public ComboboxItem(string t, short v)
{
Text = t;
Value = v;
}
}
The combo box is bound to a list containing anonymous types. You ought to use the dynamic keyword.
dynamic item = cbo.SelectedItem;
String text = item.Text;
Int32 value = item.Value;
You should add this.cbo.SelectedItem as object;
Then, for example:
public class student
{
public string name;
public int age;
}
var stu = cbo.SelectedItem as student;
string name = stu.name;
int age = stu.age;
OK,this is my first answer.
create class with Text and Value properties (ComboboxItem), then create the item list with that class. now you can do as below
ComboboxItem obj = cbo.SelectedItem as ComboboxItem;
//now you can get the obj.Value
I notice you're blanking out certain parts of your code, as of such I shall assume you're not using the object 'object' but something else, else your code wouldn't compile.
The ComboBox does not hold the datatype of its values, it all treats them as simple objects. So SelectedItem will be of type object, which should then be casted to the correct datatype in order to access the text / value property.
var myItem = cbo.SelectedItem as MyObject
if(myItem != null){
Console.WriteLine("Value is {0}", myItem.Value);
}
I'm trying to display using a DataGridView and I'm getting some strange results.
When I set the data source with an anonymous type like so:
var displayList = CreateAnAnonymousBindingList(new { prop1 = string. Empty ...etc... } );
displayList.AllowNew = true; //The property in the DataGridView is set in the designer
var list = from someEntity in entities.EntityGroup //I want some of the fields from each entity
select new { prop1 = someEntity.prop1...etc...};
foreach(item in list)
{
displayList.add(item);
}
form.dataGridView.DataSource = displayList;
The data I want is displayed, but I cannot add new items, there is an exception caused by the anonymous type. This, I know, is because it is an anonymous type and has no constructors.
The problem is, when I create a concrete class using the same types, even names as the anonymous type, create a BindingList (simply by new BindingList()) and add items to it like:
BindingList<ClassName> displayList = new BindingList<ClassName>();
displayList.AllowNew = true;
var list = from someEntity in entities.EntityGroup
select someEntity;
foreach(var item in list)
{
ClassName temp = new ClassName();
/* Assign all the properties I want*/
displayList.Add(temp);
}
form.dataGridView.DataSource = displayList;
Nothing is displayed, even though the list has items in it, and the data source is set to the list. I cannot work out why this is happening, maybe I'm overlooking something really, really simple, but I cannot see where the issue is coming from.
Any help would be fantastic.
Change your class to use properties and datagridview will display the list.
class ClassName
{
public string ID { get; set; }
public string Name { get; set; }
}
Let's say I have a ListBox called animalList. As DataSource I use following class:
class Animal
{
private int id;
private string name;
private string description;
public Animal(int id, string name, string description)
{
// implementation
}
public int Id
{
// implementation
}
public string Name
{
// implementation
}
public string Description
{
// implementation
}
}
I'd like to have 2 columns in ListBox: Name and Description. Is it possible to do so?
I managed to add one column like this:
List<Animal> animals = // LINQ sucking data from XML
animalList.MultiColumn = true;
animalList.DataSource = animals;
animalList.DisplayMember = "Name";
animalList.ValueMember = "Id";
but I cannot really figure out how to actually implement next column.
The name of the MultiColumn property can be slightly misleading. The ListBox control does not support the type of columns you're looking for.
What MultiColumn actually does is "overflow" items into a new column instead of showing a vertical scrollbar.
http://msdn.microsoft.com/en-us/library/system.windows.forms.listbox.multicolumn.aspx