DataLink Example

This example shows how to enable the two directional communication between an Access DataBase and a Text File.

The Problem

For example if you want to read/write records from/to the Orders table (from the Northwind DB)

 

To use Delimited Format

You must define:

[DelimitedRecord("|")] public class OrdersVerticalBar { public int OrderID; public string CustomerID; public int EmployeeID; public DateTime OrderDate; public DateTime RequiredDate; [FieldNullValue(typeof(DateTime), "2005-1-1")] public DateTime ShippedDate; public int ShipVia; public decimal Freight; }

To use FixedLength Format

You must define:

[FixedLengthRecord] public class OrdersFixed { [FieldFixedLength(7)] public int OrderID; [FieldFixedLength(12)] public string CustomerID; [FieldFixedLength(3)] public int EmployeeID; [FieldFixedLength(10)] public DateTime OrderDate; [FieldFixedLength(10)] public DateTime RequiredDate; [FieldFixedLength(10)] [FieldNullValue(typeof(DateTime), "2005-1-1")] public DateTime ShippedDate; [FieldFixedLength(3)] public int ShipVia; [FieldFixedLength(10)] public decimal Freight; }

The DataLinkClass

How you can see in the Class Diagram you must inherit from AccessStorage or SqlServerStorage to finish the DataLink.

In this example we use the first one, and the resulting code is:

AccessStorage storage = new AccessStorage(typeof(OrdersFixed), "TestData.mdb"); storage.SelectSql = "SELECT * FROM Orders"; storage.FillRecordCallback = new FillRecordHandler(FillRecordOrders); FileDataLink.EasyExtractToFile(storage, "out.txt");

The Code of the FillRecordOrders

protected void FillRecordOrders(object rec, object[] fields) { OrdersFixed record = (OrdersFixed) rec; record.OrderID = (int) fields[0]; record.CustomerID = (string) fields[1]; record.EmployeeID = (int) fields[2]; record.OrderDate = (DateTime) fields[3]; record.RequiredDate = (DateTime) fields[4]; if (fields[5] != DBNull.Value) record.ShippedDate = (DateTime) fields[5]; else record.ShippedDate = DateTime.MinValue; record.ShipVia = (int) fields[6]; record.Freight = (decimal) fields[7]; }

 

Sample output/input to this code:

10248|VINET|5|04071996|01081996|16071996|3|32.38 10249|TOMSP|6|05071996|16081996|10071996|1|11.61 10250|HANAR|4|08071996|05081996|12071996|2|65.83 10251|VICTE|3|08071996|05081996|15071996|1|41.34 10252|SUPRD|4|09071996|06081996|11071996|2|51.3 10253|HANAR|3|10071996|24071996|16071996|2|58.17 10254|CHOPS|5|11071996|08081996|23071996|2|22.98 10255|RICSU|9|12071996|09081996|15071996|3|148.33 ....

See also

Must Read - Quick Start Guide - Attributes List - F.A.Q. - Examples of Use - Contacts & Credits - Donations

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