Creating a dataset structure manually

protected DataSet CreatePurchaseRequestStructure()
{
DataSet dsPurchaseRequestItem = new DataSet();
DataTable dt = new DataTable();
dsPurchaseRequestItem.Tables.Add(dt);
DataColumn dcItemId = new DataColumn("ItemId");
DataColumn dcItem = new DataColumn("Item");
DataColumn dcSupplierId = new DataColumn("SupplierId");
DataColumn dcSupplier = new DataColumn("Supplier");
DataColumn dcUnitId = new DataColumn("UnitId");
DataColumn dcUnit = new DataColumn("Unit");
DataColumn dcRequestedQuantity = new DataColumn("RequestedQuantity");
DataColumn dcCurrentStock = new DataColumn("CurrentStock");
DataColumn dcMinimumReorderQuantity = new DataColumn("MinimumReorderQuantity");
DataColumn dcPendingQuantity = new DataColumn("PendingQuantity");

dsPurchaseRequestItem.Tables[0].Columns.Add(dcItemId);
dsPurchaseRequestItem.Tables[0].Columns.Add(dcItem);
dsPurchaseRequestItem.Tables[0].Columns.Add(dcSupplierId);
dsPurchaseRequestItem.Tables[0].Columns.Add(dcSupplier);
dsPurchaseRequestItem.Tables[0].Columns.Add(dcUnitId);
dsPurchaseRequestItem.Tables[0].Columns.Add(dcUnit);
dsPurchaseRequestItem.Tables[0].Columns.Add(dcRequestedQuantity);
dsPurchaseRequestItem.Tables[0].Columns.Add(dcCurrentStock);
dsPurchaseRequestItem.Tables[0].Columns.Add(dcMinimumReorderQuantity);
dsPurchaseRequestItem.Tables[0].Columns.Add(dcPendingQuantity);
return dsPurchaseRequestItem;
}

Filtering from dataset

public void LoadItems()
{
dsItems = InventoryManager.ListItems();
if (dsItems.Tables[0].Rows.Count.Equals(0))
{
DataRow drNew = dsItems.Tables[0].NewRow();
dsItems.Tables[0].Rows.Add(drNew);
GridView1.DataSource=dsItems;
GridView1.DataBind();
grvItem.Rows[0].Visible = false;
}
else
{
DataView dv;
if (ViewState["sortExpr"] != null)
{
dv = new DataView(dsItems.Tables[0]);
dv.Sort = (string)ViewState["sortExpr"];

}
else
{
dv = new DataView(dsItems.Tables[0]);
}
dv.RowFilter = "Name like '%" + txtSearch.Text + "%'";
GridView1.DataSource=dv;
GridView1.DataBind();
}
}