if(!page.ispostback())
{ ((DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("ddlTestType")).Items.Clear();
((DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl
("ddlTestType")).DataSource = TestTypeSectionManager.getTestTypes();
Try this.
<pre>((DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("ddlTestType")).datatextfield = "TestTypesName"
((DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("ddlTestType")).datavaluefield = "TestTypesId"
((DropDownList)RegisterUser.CreateUserStep.ContentTemplateContainer.FindControl("ddlTestType")).DataBind();
}