如何使用清单 <Hashtable> 从C＃

Question

How to store and retrieve values from List in C#? I can store values like this

List<Hashtable> mList=new List<Hashtable>();
Hashtable ht = new Hashtable();
ht.Add(1, "One");
ht.Add(2, "Two");
ht.Add(3, "Three");
ht.Add(4, "Four");
mList.Add(ht);

How to set these values to base adapter textview in C#?

Answer 1

How to set these values to base adapter textview in C#?

I assume that your base adapter means the BaseAdapter for a ListView , then you can create a adapter inherit from BaseAdapter for example like this:

public class MainAdapter : BaseAdapter<Hashtable>
{
    private List<Hashtable> items;
    private Activity context;

    public MainAdapter(Activity context, List<Hashtable> items) : base()
    {
        this.context = context;
        this.items = items;
    }

    public override Hashtable this[int position]
    {
        get
        {
            return items[position];
        }
    }

    public override int Count
    {
        get
        {
            return items.Count;
        }
    }

    public override long GetItemId(int position)
    {
        return position;
    }

    public override View GetView(int position, View convertView, ViewGroup parent)
    {
        View view = convertView;
        if (view == null)
            view = context.LayoutInflater.Inflate(Android.Resource.Layout.SimpleListItem1, null);
        view.FindViewById<TextView>(Android.Resource.Id.Text1).Text = items[position].ToString();
        return view;
    }
}

and use the List<HashTable> for your adapter like this:

public class MainActivity : ListActivity
{
    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        //SetContentView(Resource.Layout.Main);

        List<Hashtable> mList = new List<Hashtable>();
        Hashtable ht = new Hashtable();
        ht.Put(1, "One");
        ht.Put(2, "Two");
        ht.Put(3, "Three");
        ht.Put(4, "Four");
        mList.Add(ht);

        ListAdapter = new MainAdapter(this, mList);
    }
}

But I doubt this is really what you need. You have only one item in List<> and this item has one Hashtable which contains four key-pair value. Is it possible that you need a key-pair value to be shown on each item of ListView instead of showing four key-pair values in one item?

I do agree with @Henk Holterman, it is very strange to put an old-style hashtable in a List<> , if you want to use List<> to store multiple string values with key, you can simply code like this:

List<string> mList = new List<string>();
mList.Add("One");
mList.Add("Two");
mList.Add("Three");
mList.Add("Four");

List<> itself allocates a index for each item, for example, if you want to find the index of string item "Three", you can code like this:

var index = mList.IndexOf("Three");

Since the first item in List<> will match the index of 0, here the index of item "Three" will be 2.

Of course I'm not saying it is not allowed to store a Hashtable into a List<> , but usually when we want to define a Key for each item, one method is to create a class model, for example:

public class MyListModel
{
    public int Key { get; set; }
    public string Content { get; set; }
}

And now you can create a List<> for this model:

List<MyListModel> mList = new List<MyListModel>();
for (int i = 1; i <= 10; i++)
{
    mList.Add(new MyListModel { Key = i, Content = "item " + i });
}

The advantage to use a data model for ListView is that if your each ListView item has for example more than one TextView , each is for displaying different information, then you can simply add those properties in this class model.

For more information of building a ListView in Xamarin.Android, you can refer to ListViews and Adapters .