/// <summary>
/// 删除指定位置的文字，从(0,0)开始
/// </summary>
/// <param name="startLine"></param>
/// <param name="startCol"></param>
/// <param name="endLine"></param>
/// <param name="endCol"></param>
public void DeleteText(int startLine, int startCol, int endLine, int endCol)
{
EditPoint editPoint = GetEditPoint(startLine, startCol);
if (editPoint != null)
{
object tp;
TextLines.CreateTextPoint(endLine, endCol, out tp);
editPoint.Delete(tp as TextPoint);
}
}