//自适应列宽
this.dgvBaoming.AutoSizeColumnsMode = System.Windows.Forms.DataGridViewAutoSizeColumnsMode.AllCells;
//平铺均分列宽
this.dgvBaoming.AutoSizeColumnsMode = System.Windows.Forms.DataGridViewAutoSizeColumnsMode.Fills;
原文：https://www.cnblogs.com/Striveyoungfellow/p/12490489.html