Data source is an invalid type

Question

i got error as 

Data source is an invalid type. It must be either an IListSource, IEnumerable, or IDataSource.

  BL b = new BL();

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)

{

string X = Convert.ToString(e.CommandArgument);

int index = Convert.ToInt32(X);

GridViewRow row = (GridViewRow)GridView1.Rows[index];

Label id = (Label)row.FindControl("lbl1");

int artid = Convert.ToInt32(id.Text);

GridView1.DataSource =b.DeleteProList(artid);

GridView1.DataBind();

} 

 

DAL:

public int DeleteProList(int proId)

{

con.Open();

SqlCommand cmd = new SqlCommand("sp_deleteProjectList", con);

cmd.CommandType = CommandType.StoredProcedure;

cmd.Parameters.AddWithValue("@ProjectId", proId);

SqlDataAdapter da = new SqlDataAdapter(cmd);

DataSet ds = new DataSet();

da.Fill(ds);

int i = Convert.ToInt32(cmd.ExecuteNonQuery());

return i;

}

 

BL:

public int DeleteProList(int proId)

{

return d.DeleteProList(proId);

}