为什么我不能在BindingSource上挂起绑定？

First, the offending code:

首先，违规代码：

public virtual void grid_RefreshFetchData(Object sender, RefreshEventArgs e)
{
    C1DBGrid g = (C1DBGrid)sender;
    if (g.RefreshUseResult)
    {
        DataTable dtNew = FetchRawData(e.Argument);
        dt_Patch(dtNew, e.Argument);
        g.BindingSource.SuspendBinding();
        ((DataTable)g.BindingSource.DataSource).Clear();
        ((DataTable)g.BindingSource.DataSource).Merge(dtNew);
        g.BindingSource.ResumeBinding();
    }
}
public