C# 4 and .NET 4

1130 ❘ ChaPTer 39 windOws fOrms
The form consists of the getData button, which when clicked calls the getData_Click() method shown in
the example code.
This constructs a SqlConnection object, using the ConnectionStrings property of the
ConfigurationManager class. Subsequently, a data set is constructed and filled from the database table,
using a DataAdapter object. The data is then displayed by the DataGridView control by setting the
DataSource and DataMember properties. Note that the AutoGenerateColumns property is also set to true
because this ensures that something is displayed to the user. If this flag is not specified, you need to create all
the columns yourself.
Data sources
The DataGridView control provides a flexible way to display data; in addition to setting the DataSource to
a DataSet and the DataMember to the name of the table to display, the DataSource property can be set to
any of the following sources:
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An array (the grid can bind to any one-dimensional array)
DataTable
DataView
DataSet or DataViewManager
Components that implement the IListSource interface
Components that implement the IList interface
Any generic collection class or object derived from a generic collection class
The following sections give an example of each of these data sources.
Displaying Data from an array
At first glance, displaying data from an array seems to be easy. Create
an array, fill it with some data, and set the DataSource property on the
DataGridView control. Here’s some example code:
string[] stuff = new string[] {"One", "Two", "Three"};
dataGridView.DataSource = stuff;
If the data source contains multiple possible candidate tables (such as
when using a DataSet or DataViewManager), you need to also set the
DataMember property.
You could replace the code in the previous example’s getData_Click
event handler with the preceding array code. The problem with this
code is the resulting display (see Figure 39-3).
Instead of displaying the strings defined within the array, the grid displays the length of those strings. That’s
because when using an array as the source of data for a DataGridView control, the grid looks for the first
public property of the object within the array and displays this value rather than the string value. The first
(and only) public property of a string is its length, so that is what is displayed. The list of properties for
any class can be obtained by using the GetProperties method of the TypeDescriptor class. This returns
a collection of PropertyDescriptor objects, which can then be used when displaying data. The .NET
PropertyGrid control uses this method when displaying arbitrary objects.
One way to rectify the problem with displaying strings in the DataGridView is to create a wrapper class:
protected class Item
{
public Item(string text)
{
_text = text;
}
figure 39-3
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