DataGridView empty the original data

WinForm used in the DataGridView, in the implementation of the query function, and rebind the result data source process, found that Datagirdview did not empty the original data, but the results are automatically added below the original data.
At first I set the DataGridView data source to null: DataGridView. Datasource=null; but found no use.
DataGridView was used again. Rows.clear (), the result is wrong and you are prompted to "cannot clear this list."
In the online search, the original data source binding DataGridView can not be purged with rows.clear (), or by setting the data source to null, only manually added data can be emptied.
Later I used the online thought of the method of predecessors, can maintain the original column:
The original data of the binding
DataTable dt=new DataTable ();
DataGridView. DATASOURCE=DT;


Clear the original data
Dt. Rows.clear ();
DataGridView. DATASOURCE=DT;