title: SetBackgroundColor to listview item on Custom Adapter does not work
body: <p>I have a working Custom Adapter that I have put to a listview.<br>
  I now add 15 items successfully.</p>
  
  <p>I now try to set the background color on item 3 to orange. 
  This work!</p>
  
  <p>However when I scroll down and up, the background color dissapears.<br>
  How can we prevent this?</p>
  
  <p>//MENU.axml with the listview1
  <div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>MENU.axml
  &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:background="#70292929"
      android:layout_gravity="top|right"
      android:orientation="horizontal"&gt;
        &lt;ListView
            android:id="@+id/listview1"
            android:background="#1b4f72"
            android:layout_weight="0.5"
            android:layout_gravity="top|left"
            android:layout_width="10px"
            android:layout_height="match_parent"&gt;
        &lt;/ListView&gt;
  &lt;/LinearLayout&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>//C# code to add items to the listview1 and try to set the background on item 3 to orange</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>Android.Views.View MENUVIEW = LayoutInflater.Inflate(Resource.Layout.MENU, null);
  ListView LISTVIEW1 = MENUVIEW.FindViewById&lt;ListView&gt;(Resource.Id.listview1);
  
                  //Add Items to the listview1
                  List&lt;String&gt; itemLIST = new List&lt;String&gt;(); 
                  for (int i = 0; i &lt; 15; i++)
                  {
                      itemLIST.Add("hello" + i); 
                  }
                  Adapter1 adapter1 = new Adapter1(this, Android.Resource.Layout.SimpleListItem1, itemLIST);
                  LISTVIEW1.Adapter = adapter1;
  
  //Set backgroundcolor on item 3
  LISTVIEW1.GetChildAt(3).SetBackgroundColor(Android.Graphics.Color.Orange);
  TextView tview = listview.GetChildAt(3).FindViewById&lt;TextView&gt;(Resource.Id.itemtext);
  tview.SetBackgroundColor(Android.Graphics.Color.Orange);</code></pre>
  </div>
  </div>
  </p>
  
  <p>//Code for the Adapter1</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>   class Adapter1 : BaseAdapter
      {
  
          Context context;
          int item = 0;
          List&lt;String&gt; items = new List&lt;String&gt;();
  
          public Adapter1(Context context, int resource, List&lt;String&gt; itemArray)
          {
              items = itemArray;
              item = resource;
              this.context = context;
          }
     
  
          public override Java.Lang.Object GetItem(int position)
          {
              return position;
          }
  
          public override long GetItemId(int position)
          {
              return position;
          }
          
          public String getItem(int position)
          {
              return items[position]; //returns list item at the specified position
          }
          public override int GetItemViewType(int position)
          {
              return position;
          }
          
  
          public override View GetView(int position, View convertView, ViewGroup parent)
          {
              var view = convertView;
              Adapter1ViewHolder holder = null;
             
  
              if (holder == null)
              {
                  holder = new Adapter1ViewHolder();
                  var inflater = context.GetSystemService(Context.LayoutInflaterService).JavaCast&lt;LayoutInflater&gt;();
  
                  view = inflater.Inflate(Resource.Layout.textview, parent, false);
                  String currentItem = getItem(position);
  
                  //get the TextView for item name and item description
                  TextView textViewItemName = view.FindViewById&lt;TextView&gt;(Resource.Id.itemtext);
  
                  //sets the text for item name and item description from the current item object
                  textViewItemName.SetText(currentItem, TextView.BufferType.Normal);
  
                  holder.Title = textViewItemName;
                  holder.Title.Text = currentItem;
                  view.Tag = holder;
              }
              return view;
          }
  
          //Fill in cound here, currently 0
          public override int Count
          {
              get
              {
                  return items.Count;
              }
          }
      }
  
      class Adapter1ViewHolder : Java.Lang.Object
      {
          //Your adapter views to re-use
          public TextView Title { get; set; }
      }</code></pre>
  </div>
  </div>
  </p>