Virtualizing DataGrid over ListCollectionView - wpf

Question

I am using a ListCollectionView over a custom list which provides read access to a particular database table. Below is the definition of the custom list.
class MaterialCollection : IList
{
#region Fields
private Object syncRoot;
private SQLiteConnection connection;
#endregion
#region IList Interface
public object this[int index]
{
get
{
using (SQLiteCommand command = connection.CreateCommand())
{
command.CommandText = "SELECT * FROM Materials LIMIT 1 OFFSET #Index";
command.Parameters.AddWithValue("#Index", index);
using (SQLiteDataReader reader = command.ExecuteReader())
{
if (reader.Read())
{
return GetMaterial(reader);
}
else
{
throw new Exception();
}
}
}
}
set
{
throw new NotImplementedException();
}
}
public int Count
{
get
{
using (SQLiteCommand command = connection.CreateCommand())
{
command.CommandText = "SELECT Count(*) FROM Materials";
return Convert.ToInt32(command.ExecuteScalar());
}
}
}
public bool IsFixedSize
{
get
{
return false;
}
}
public bool IsReadOnly
{
get
{
return true;
}
}
public bool IsSynchronized
{
get
{
return true;
}
}
public object SyncRoot
{
get
{
return this.syncRoot;
}
}
public IEnumerator GetEnumerator()
{
return Enumerate().GetEnumerator();
}
#endregion
#region Constructor
public MaterialCollection(SQLiteConnection connection)
{
this.connection = connection;
this.syncRoot = new Object();
}
#endregion
#region Private Methods
private Material GetMaterial(SQLiteDataReader reader)
{
int id = Convert.ToInt32(reader["Id"]);
string materialNumber = Convert.ToString(reader["MaterialNumber"]);
string type = Convert.ToString(reader["Type"]);
string description = Convert.ToString(reader["Description"]);
string alternateDescription = Convert.ToString(reader["AlternateDescription"]);
string tags = Convert.ToString(reader["Tags"]);
Material material = new Material();
material.Id = id;
material.MaterialNumber = materialNumber;
material.Type = (MaterialType)Enum.Parse(typeof(MaterialType), type);
material.Description = description;
material.AlternateDescription = alternateDescription;
material.Tags = tags;
return material;
}
private IEnumerable<Material> Enumerate()
{
using (SQLiteCommand command = connection.CreateCommand())
{
command.CommandText = "SELECT * FROM Materials";
using (SQLiteDataReader reader = command.ExecuteReader())
{
while (reader.Read())
{
yield return GetMaterial(reader);
}
}
}
}
#endregion
#region Unimplemented Functions
public int Add(object value)
{
throw new NotImplementedException();
}
public void Clear()
{
throw new NotImplementedException();
}
public bool Contains(object value)
{
throw new NotImplementedException();
}
public void CopyTo(Array array, int index)
{
throw new NotImplementedException();
}
public int IndexOf(object value)
{
return 0;
}
public void Insert(int index, object value)
{
throw new NotImplementedException();
}
public void Remove(object value)
{
throw new NotImplementedException();
}
public void RemoveAt(int index)
{
throw new NotImplementedException();
}
#endregion
}
The problem is that during the initial population of the DataGrid, the this[int index] method is called for every single row (i.e. 0 through Count - 1).
As the table contains potentially millions of rows and read operations are costly (i.e. SQLite on a legacy HDD), such an operation is unacceptable. Furthermore, it doesn't make sense to load all of the millions of rows when the screen can only accommodate for 50 or so items.
I would like to make it such that the DataGrid fetches only the row that it is displaying, instead of fetching the entire table. How is such a working possible?
(P.S. I have ensured that virtualizatin is enabled for the DataGrid itself)

Answer 1

It seems that the problem was resolved after adding ScrollViewer.CanContentScroll="True" to the ListView.