Improve VFP data retrieval with WCF

Windows Communication Foundation (WCF) enables us to create distributed architecture and use Visual FoxPro (VFP) as a client/server system executing the operation on the server (backend). With the WCF client we can download the data from the server in asynchronous (non blocking) mode. The measurement in this article show us this can be done much faster then downloading the data with VFP functions or oledb data adapters. With WCF, we can take advantage of parallel (asynchronous) operation and distribute the processing of data between the client and the server. The retrieved data can be presented in VFP or Net (Windows) controls. In the download of this article is the code of four projects: WCF service, WCF client, COM object and VFP client. We present the code and the measurement of retrieving the data from the server in the form of a data table, a dataset, a strong typed collection and the dbf file. The fastest is the retrieve and transport of the dbf file binded to the VFP grid, on the second place (24%slower) is the strong typed Net collection binded to the Net grid, the laziest (30% slower) is the Net data table binded to the windows Net grid. Except for very small record set, there is a big time gap (almost 100%) between the direct VFP data retrive over the local network and using the WCF service.

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VFP performance in LAN environment

Visual FoxPro is one the fastest performing desktop and LAN-based database management system available today. But opening large tables creates a great deal of network traffic. This can be a substantial delay, sometimes beyond an acceptable length of time. In this article I present the results of the VFP speed measurement in the process of acquiring database data with different VFP9 methods. The store procedures, duplicated records and unique indexes enriched by the programmers’ knowledge of the database organization can speed up the data query. With the stored procedure we can fetches the result set of 100 records from the server about 100% faster than with the full optimized SQL command. Changing the table’s normalization and using appropriate indexes, we can improve the retrieval time for 275%.

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Periodical Asynchronous Requests in VFP Forms

Creating a client (VFP) application, which would be continuously calling the server for data changes on the server in asynchronous (no blocking) mode, would be difficult or perhaps even impossible to do in VFP. In this article I present a COM object in C# which downloads the data from the network computer in asynchronous mode and periodically refresh the controls on the VFP form.

Author: Josip Zohil, Koper, Slovenija, mailto:Josip.Zohil1@guest.arnes.si

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