ToList Method
The ToList method converts all rows in a data table into list of elements.
Namespace: PocoDataSet.Extensions
Assembly: PocoDataSet.Extensions.dll
The first overload produces an list of "live" objects. Any change made through the interface is immediately reflected in the underlying data row:
/// <summary>
/// Converts all rows in the specified data table to a list of interface proxies.
/// </summary>
/// <typeparam name="TInterface">The interface type describing the table's row contract.</typeparam>
/// <param name="dataTable">Data table</param>
/// <returns>A list of TInterface proxies backed by data rows.</returns>
public static List<TInterface> ToList<TInterface>(this IDataTable? dataTable) where TInterface : class
Assuming that there is an interface IEmploymentType, which defines employment type functionality:
/// <summary>
// Defines employment type functionality
/// </summary>
public interface IEmploymentType
{
int Id { get; set; }
string Code { get; set; }
string? Description { get; set; }
}
// 1. Create data set
IDataSet dataSet = DataSetFactory.CreateDataSet();
// 2. Add employment type table to data set
IDataTable employmentTypeDataTable = dataSet.AddNewTable("EmploymentType");
employmentTypeDataTable.AddColumn("Id", DataTypeNames.INT32);
employmentTypeDataTable.AddColumn("Code", DataTypeNames.STRING);
employmentTypeDataTable.AddColumn("Description", DataTypeNames.STRING);
// 3. Add several rows to employment type table
IDataRow employmentTypeDataRow1 = employmentTypeDataTable.AddNewRow();
employmentTypeDataRow1["Id"] = 1;
employmentTypeDataRow1["Code"] = "ET01";
employmentTypeDataRow1["Description"] = "Full Time";
IDataRow employmentTypeDataRow2 = employmentTypeDataTable.AddNewRow();
employmentTypeDataRow2["Id"] = 2;
employmentTypeDataRow2["Code"] = "ET02";
employmentTypeDataRow2["Description"] = "Part Time";
// 4. Call ToList method to get live proxies backed by IDataRow
List<IEmploymentType> employmentTypes = employmentTypeDataTable.ToList<IEmploymentType>();
// 5. Change data of the second row through the interface
employmentTypes[1].Description = "Contractor";
The second overload produces either "live" or detached results, depending entirely on what the selector delegate returns.
/// <summary>
/// Converts all rows in the specified data table to an list of elements using a custom selector.
/// </summary>
/// <typeparam name="T">The element type of the resulting list.</typeparam>
/// <param name="dataTable">Data table</param>
/// <param name="selector">A delegate that creates an element of specified type from a data row.</param>
/// <returns>An list of elements created from each row.</returns>
public static List<T> ToList<T>(this IDataTable? dataTable, Func<IDataRow, T> rowSelectionFunction)
If the selector returns an interface proxy created from the row (for example, via AsInterface<TInterface>()),
the resulting list contains objects backed by IDataRow. Setting a property updates the underlying row immediately.
// 1. Create data set
IDataSet dataSet = DataSetFactory.CreateDataSet();
// 2. Add employment type table to data set
IDataTable employmentTypeDataTable = dataSet.AddNewTable("EmploymentType");
employmentTypeDataTable.AddColumn("Id", DataTypeNames.INT32);
employmentTypeDataTable.AddColumn("Code", DataTypeNames.STRING);
employmentTypeDataTable.AddColumn("Description", DataTypeNames.STRING);
// 3. Add several rows to employment type table
IDataRow employmentTypeDataRow1 = employmentTypeDataTable.AddNewRow();
employmentTypeDataRow1["Id"] = 1;
employmentTypeDataRow1["Code"] = "ET01";
employmentTypeDataRow1["Description"] = "Full Time";
IDataRow employmentTypeDataRow2 = employmentTypeDataTable.AddNewRow();
employmentTypeDataRow2["Id"] = 2;
employmentTypeDataRow2["Code"] = "ET02";
employmentTypeDataRow2["Description"] = "Part Time";
// 4. Call ToList method providing the selector to get live proxies backed by IDataRow
List<IEmploymentType> employmentTypes = employmentTypeDataTable.ToList(row => row.AsInterface<IEmploymentType>());
// 5. Change data of the second row through the interface
employmentTypes[1].Description = "Contractor";
If the selector returns IDataRow (or another row-backed wrapper), the result is live because you still hold
direct references to the rows in the table.
// 1. Create data set
IDataSet dataSet = DataSetFactory.CreateDataSet();
// 2. Add employment type table to data set
IDataTable employmentTypeDataTable = dataSet.AddNewTable("EmploymentType");
employmentTypeDataTable.AddColumn("Id", DataTypeNames.INT32);
employmentTypeDataTable.AddColumn("Code", DataTypeNames.STRING);
employmentTypeDataTable.AddColumn("Description", DataTypeNames.STRING);
// 3. Add several rows to employment type table
IDataRow employmentTypeDataRow1 = employmentTypeDataTable.AddNewRow();
employmentTypeDataRow1["Id"] = 1;
employmentTypeDataRow1["Code"] = "ET01";
employmentTypeDataRow1["Description"] = "Full Time";
IDataRow employmentTypeDataRow2 = employmentTypeDataTable.AddNewRow();
employmentTypeDataRow2["Id"] = 2;
employmentTypeDataRow2["Code"] = "ET02";
employmentTypeDataRow2["Description"] = "Part Time";
// 4. Call ToList method providing the selector to get table rows
List<IDataRow> rows = employmentTypeDataTable.ToList(row => row);
// 5. Change data of the second row
rows[1]["Description"] = "Contractor";
If the selector creates a new object (for example, a DTO/POCO) and copies values from the row, the resulting list is a snapshot. Changing the returned objects does not affect the table, and later table changes are not reflected in the returned objects.
Assuming that there is a class which implements interface IEmploymentType:
/// <summary>
// Provides employment type functionality
/// </summary>
public class EmploymentType : IEmploymentType
{
public int Id { get; set; }
public string Code { get; set; }
public string? Description { get; set; }
}
// 1. Create data set
IDataSet dataSet = DataSetFactory.CreateDataSet();
// 2. Add employment type table to data set
IDataTable employmentTypeDataTable = dataSet.AddNewTable("EmploymentType");
employmentTypeDataTable.AddColumn("Id", DataTypeNames.INT32);
employmentTypeDataTable.AddColumn("Code", DataTypeNames.STRING);
employmentTypeDataTable.AddColumn("Description", DataTypeNames.STRING);
// 3. Add several rows to employment type table
IDataRow employmentTypeDataRow1 = employmentTypeDataTable.AddNewRow();
employmentTypeDataRow1["Id"] = 1;
employmentTypeDataRow1["Code"] = "ET01";
employmentTypeDataRow1["Description"] = "Full Time";
IDataRow employmentTypeDataRow2 = employmentTypeDataTable.AddNewRow();
employmentTypeDataRow2["Id"] = 2;
employmentTypeDataRow2["Code"] = "ET02";
employmentTypeDataRow2["Description"] = "Part Time";
// 4. Call ToList method providing the selector to get stand alone POCOs
List<EmploymentType> employmentTypes = employmentTypeDataTable.ToList(row => row.ToPoco<EmploymentType>());
// Case 1: Row field value does not change if POCO property changes
employmentTypes[0].Description = "Contractor";
// Case 2: POCO property does not change if row field value changes
employmentTypeDataTable.Rows[1]["Description"] = "Contractor";
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Business Process Programming in .Net
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