这样的例子还有很多。你可以试试这个教程。
在Visual Studio中创建新项目。

using System;
using System.Windows.Forms;    
using System.Runtime.InteropServices;    
using Excel = Microsoft.Office.Interop.Excel;            
namespace WindowsFormsApplication4    
{    
    public partial class Form1 : Form   
    {   
        public Form1()  
        {
            InitializeComponent();    
        }
        private void button1_Click(object sender, EventArgs e)    
        {   
            Excel.Application xlApp ;  
            Excel.Workbook xlWorkBook ; 
            Excel.Worksheet xlWorkSheet ;  
            Excel.Range range ;   
            string str;
            int rCnt ;
            int cCnt ;
            int rw = 0;
            int cl = 0;
            xlApp = new Excel.Application();
            xlWorkBook = xlApp.Workbooks.Open(@"d:\csharp-Excel.xls", 0, true, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);
            xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);
            range = xlWorkSheet.UsedRange;
            rw = range.Rows.Count;
            cl = range.Columns.Count;
            for (rCnt = 1; rCnt  < = rw; rCnt++)
            {
                for (cCnt = 1; cCnt  < = cl; cCnt++)
                {
                    str = (string)(range.Cells[rCnt, cCnt] as Excel.Range).Value2;
                    MessageBox.Show(str);
                }
            } 
            xlWorkBook.Close(true, null, null);
            xlApp.Quit();
            Marshal.ReleaseComObject(xlWorkSheet);
            Marshal.ReleaseComObject(xlWorkBook);
            Marshal.ReleaseComObject(xlApp);
        }
    }
}

它需要添加Microsoft Excel 15。0对象库到您的项目。
教程链接：http://csharp.net-informations.com/excel/csharp-read-excel.htm