值在列表框中显示为类名称

Question

I'm reading in a field from a database into a list, like so

PaceCalculator pace = new PaceCalculator();
List<PaceCalculator> Distancelist = new List<PaceCalculator>();
while (Reader.Read()) //Loops through the database and adds the values in EventDistance to the list
{
    pace.Distance = (int)Reader["EventDistance"];
    Distancelist.Add(pace);
} 

I want to put the values into a listbox, but when I do it like this:

listBox1.DataSource = Distancelist;

It only shows the class name, which is PaceCalculator . It shows the right number of values, it just shows the class name instead. I want to see the integers in there.

Answer 1

You have two options,

• Override ToString in your class to return the required string
• or , if you only want to display Distance then specify that as DisplayMember

like:

listBox1.DisplayMember = "Distance";
listBox1.DataSource = Distancelist;

This will display you the Distance element from your list. Or you can override ToString in your class PaceCalculator like:

public override string ToString()
{
    return string.Format("{0},{1},{2}", property1, property2, property3);
}

EDIT:

Based on your comment and looking at your code, You are doing one thing wrong.

this only displays the last value in the list, 46, 8 times

You are adding the same instance ( pace ) of your class in your list on each iteration. Thus it is holding the last value (46) . You need to instantiate a new object in the iteration like:

while (Reader.Read()) 
{
    PaceCalculator pace = new PaceCalculator();
    pace.Distance = (int)Reader["EventDistance"];
    Distancelist.Add(pace);
} 

Answer 2

Specify the property of PaceCalculator to display.

listBox1.DataSource = Distancelist;
listBox1.DisplayMember = "Distance";

The ListBox control allows you to pick a property from the collection to display to the user.

There's also a ValueMember property that allows you to specify the value for each item in the ListBox . Assuming your data included an id called "SomeUniqueRecordId", for instance:

listBox1.ValueMember = "SomeUniqueRecordId";