Home > Posts > Creating a DataTable Index
This DataTableIndex class can be used to create an index against one or multiple DataColumns and provides a Find method that returns corresponding DataRows for a given value.
Download DataTableIndex.cs (Right Click->Save Target As...).
While trying to perform different data loads and ETL transforms you might come across the need to query a DataTable for corresponding rows for a particular column value.
The class can be used against untyped DataTables like below:
DataTable users = new DataTable();
users.Columns.Add("name");
users.Columns.Add("gender");
DataTableIndex genderIndex = new DataTableIndex(users, users.Columns["gender"]);
users.Rows.Add("John", "male");
users.Rows.Add("Mary", "female");
users.Rows.Add("George", "male");
users.Rows.Add("Lisa", "female");
foreach (DataRow female in genderIndex.Find("female"))
{
Console.WriteLine(female["name"]);
}
It can also be used against a typed DataTable. Using code behind of the DataTable an index property can even be exposed.
public partial class PurchasesDataSet
{
public partial class OrderDataTable
{
private DataTableIndex stateIndex = null;
public DataTableIndex StateIndex
{
get
{
if (stateIndex == null)
{
stateIndex = new DataTableIndex(this, this.StateColumn);
}
return stateIndex;
}
}
}
}
You can then use code like below:
PurchasesDataSet purchases = new PurchasesDataSet();
purchases.Order.AddOrderRow(
1, // OrderID
"Missouri", // State
50.25 // Total
);
purchases.Order.AddOrderRow(
2, // OrderID
"Kansas", // State
21.20 // Total
);
foreach (PurchasesDataSet.OrderRow order in purchases.Order.StateIndex.Find("Missouri"))
{
Console.WriteLine("Order ID " + order.OrderID + ": " + order.Total.ToString("c"));
}
Please send any questions or comments to Bruce Dunwiddie.
|
