效果图：
解决方案：
private double sum = 0;//取指定列的数据和，你要根据具体情况对待可能你要处理的是int
protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
{
if (e.Row.RowIndex >= 0)
{
sum += Convert.ToDouble(e.Row.Cells[6].Text);
}
else if (e.Row.RowType == DataControlRowType.Footer)
{
e.Row.Cells[5].Text = "总薪水为：";
e.Row.Cells[6].Text = sum.ToString();
e.Row.Cells[3].Text = "平均薪水为：";
e.Row.Cells[4].Text = ((int)(sum / GridView1.Rows.Count)).ToString();
}
}
后台全部代码：
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Data.SqlClient;
using System.Drawing;