主要是通过判断是否为合并单元格，和判断是否有值 ， 以及 Excel 合并单元格只去最左上的一个单元格作为合并单元格的数据 来实现该获取值的方法。
代码如下：

    private string GetCellText(int row,int col,Excel._Worksheet oSheet)
        {
            string result = "";
            bool isFound = false;
            int rowEnd = 1;
            int colEnd = 1;

            Excel.Range oRng = (Excel.Range)oSheet.Cells[row,col];
            if(oRng.Value2 != null)
            {
                result = oRng.Value2.ToString();
                isFound = true;
            }
            else
            {
                if(!(bool)oRng.MergeCells)    // 如果该单元格无值且不是合并的，则返回 null
                {
                    result = null;
                    isFound = true;
                }
            }
            if(!isFound)
            {
                // 倒序遍历该列所有行(从倒2行开始)，判断是否有合并单元格且有值，如果遇到则已求出，
                // 如果遇到非合并单元格，则行+1(倒回1行)，列同样倒序进行
                for( int r = row-1; r >=1 ;r--)
                {
                    oRng = (Excel.Range)oSheet.Cells[r,col];
                    if((bool)oRng.MergeCells)
                    {
                        try
                        {
                            if(oRng.Value2 != null)
                            {
                                result = oRng.Value2.ToString();
                                isFound = true;
                                break;
                            }
                        }
                        catch(Exception)
                        {}
                    }
                    else
                    {
                        rowEnd = r+1;
                        break;
                    }
                }
                if(!isFound)
                {
                    // 倒序遍历该行所有列，判断是否有合并单元格且有值，如果遇到则已求出，如果遇到非合并单元格，则说明数据非法。。。
                    for( int c = col-1; c >=1 ;c--)
                    {
                        oRng = (Excel.Range)oSheet.Cells[rowEnd,c];
                        if((bool)oRng.MergeCells)
                        {
                            try
                            {
                                if(oRng.Value2 != null)
                                {
                                    result = oRng.Value2.ToString();
                                    isFound = true;
                                    break;
                                }
                            }
                            catch(Exception)
                            {}
                        }
                        else
                        {
                            colEnd = c+1;
                            break;
                        }
                    }
                }
                if(!isFound)
                {
                    result = null;
                }
            }

            return result;
        }

获取值测试：

private void GetAllText()
        {
            Excel.Application oXL;
            Excel._Workbook oWB;
            Excel._Worksheet oSheet;
            object missing = System.Type.Missing;

            //创建Excel实例
            oXL = new Excel.Application();

            //打开已有的工作簿
            oWB = oXL.Workbooks.Open(@"E:\BookTest.xls",missing,missing,missing,missing,missing,missing,
                missing,missing,missing,missing,missing,missing,missing,missing);
            oSheet = (Excel.Worksheet)oWB.Sheets.get_Item(1);
            
            // 遍历获取 10行 10列 数据
            for(int i=1;i<10;i++)
            {
                for(int j=1;j<10;j++)
                {
                    string str = GetCellTest(i,j,oSheet);
                    richTextBox1.AppendText(" i : "+i.ToString() + " , j : "+ j.ToString() + " , value : "+ str +" \r\n ");
                }
            }            
        }