C# 4 and .NET 4

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}
}
SqlDataAdapter da = new SqlDataAdapter(select, conn);
Products ds = new Products();
da.Fill(ds, "Product");
foreach(Products.ProductRow row in ds.Product )
Console.WriteLine("'{0}' from {1}",
row.ProductID,
row.ProductName);
code download XSDDataSet.cs
The output of the XSD file contains a class derived from DataSet, Products, which is created and then
filled by the use of the data adapter. The foreach statement uses the strongly typed ProductRow and also
the Product property, which returns the Product data table.
To compile this example, issue the following commands:
and
xsd product.xsd /d
csc /recurse:*.cs
The first generates the Products.cs file from the Products.XSD schema, and then the csc command uses
the /recurse:*.cs parameter to go through all files with the extension .cs and add these to the resulting
assembly.
PoPulaTing a daTaseT
After you have defined the schema of your data set, replete with DataTable, DataColumn, and Constraint
classes, and whatever else is necessary, you need to be able to populate the DataSet class with some
information. You have two main ways to read data from an external source and insert it into the
DataSet class:
➤
➤
Use a data adapter.
Read XML into the DataSet class.
Populating a dataset Class with a data adapter
The section on data rows briefly introduced the SqlDataAdapter class, as shown in the following code:
string select = "SELECT ContactName,CompanyName FROM Customers";
SqlConnection conn = new SqlConnection(source);
SqlDataAdapter da = new SqlDataAdapter(select, conn);
DataSet ds = new DataSet();
da.Fill(ds, "Customers");
The bold line shows the SqlDataAdapter class in use; the other data adapter classes are again virtually
identical in functionality to the Sql equivalent.
To retrieve data into a DataSet, it is necessary to have some form of command that is executed to select that
data. The command in question could be a SQL SELECT statement, a call to a stored procedure, or for the
OLE DB provider, a TableDirect command. The preceding example uses one of the constructors available
on SqlDataAdapter that converts the passed SQL SELECT statement into a SqlCommand, and issues this
when the Fill() method is called on the adapter.
In the stored procedures example earlier in this chapter, the INSERT, UPDATE, and DELETE procedures were
defined, but the SELECT procedure was not. That gap is filled in the next section, which also shows how to
call a stored procedure from a SqlDataAdapter class to populate data in a DataSet class.
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