1-for connecting to your datasource using the SQL Server .NET Data Provider
(only for Microsoft SQL Server version 7 or above)
your string connection is something like below
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strConnection="server=YourServer;database=YourData base integrated security=<true/false>;";//also you can add your user an password
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2-for connecting to your datasource using the OLE DB.NET Data Provider
(for MS Access,Excel)
your string connection is something like below
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strConnection="Provider=Microsoft.Jet.OleDb.4.0 data
source=C:\\....\\Northwind.mdb;";//for MS Access
strConnection = "Provider=Microsoft.Jet.OleDb.4.0; data source=C:\\...\\Inventory.xls; Extended Properties=Excel 8.0;";//for Excel
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3-There are other providers for MYSQL,Oracle you can find them in
www.microsoft.com then install them,you would have some new namespaces....
(nevertheless you can connect to your MySQl,Oracle through OLE DB.NET Data Provider but it is clear which one could be better!)
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Mehdi.