The display mode of the Row Details can be specified by using the RowDetailsVisibilityMode property. It can have one of the following values:
Collapsed - row details won't be displayed for any of the rows.
Visible - row details will be displayed for each of the rows.
VisibleWhenSelected - row details will be displayed only for the selected row.
Another approach for displaying the Row Details is to use the GridViewToggleRowDetailsColumn. It will allow you to expand / collapse the Row Details for each row.
You should either use the RadGridView.RowDetailsVisibilityMode property to control the state of all grid rows or use a GridViewToggleRowDetailsColumn to control the state of each individual row. Since the GridViewToggleRowDetailsColumn operates on the respective GridViewRow.DetailsVisibilityProperty, having a RadGridView.RowDetailsVisibilityMode different from collapsed might lead to unexpected results. To learn more about this type of column read here.
You can download a runnable project demonstrating the different options from our online SDK repository here, after navigating to GridView/RowDetailsVisibilityOptions. In addition to make finding and browsing the examples easier, you can take advantage of our SDK Samples Browser.