This example shows how to edit some component properties from code. All components of the report are on pages. The pages are in the report object. In order to get a reference to the component object, you must first get a reference to the page. They can be obtained by its name. For example, change text box value in the report:
private void button2_Click(object sender, System.EventArgs e)
	stiReport1.Load("..\\Work with Components.mrt");
	((StiText)stiReport1.Pages["Page1"].Components["Text1"]).Text.Value = textBox1.Text;

In the screenshot below you can see the result of the sample code:

Working with Report Components