1、单击CheckBox列头，可实现全选和全不选的切换。 2、CheckBox列头，会根据记录的选择状态，自动呈现选中和不选中状态。 3、现在只弄了个两态的CheckBox列头，后面有时间弄个三态的。-1, click the CheckBox column headers, Select and Unselect switching.. 2, CheckBox column header will select state according to the records, aut

试定义类TRI(三角形)及其派生类COL(三角柱体).其中三角形类可以计算三角形的面积和周长:三角柱体类可以计算柱体的体积和表面积.-Try to define classes TRI (triangle) and its derived classes COL (triangular prism) which can calculate the triangle class area and perimeter of triangles: triangular prism class can

A Tri-State TreeView designed for on-demand populating of the tr-A Tri-State TreeView designed for on-demand populating of the tree