AutoCompleteTextView.txt

 //ticket load
<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:padding="10dp"
    android:textSize="16sp"
    android:textColor="#000" />


// layout items
   <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Products" />
    <AutoCompleteTextView
        android:id="@+id/autocomplete_product"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dp" />

//code need

            AutoCompleteTextView textView = FindViewById<AutoCompleteTextView>(Resource.Id.autocomplete_product);
              string[] Products = new string[] {
              "iphone 6s", "ipad", "ipad pro",
             "iphone 5", "Samsung", "Song" };
            var adapter = new ArrayAdapter<String>(this, Resource.Layout.ticket_items, Products);

             textView.Adapter = adapter;