想设置第四列为两为小数的数值

Question

导入datadridview语句:
                    string tableName = "";                    
                    string Path = ofd.FileName;
                    string strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Path + ";Extended Properties=Excel 8.0;";
                    OleDbConnection conn = new OleDbConnection(strConn);
                    conn.Open();
                    System.Data.DataTable schemaTable = conn.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Tables, null);                    
                    tableName = schemaTable.Rows[0][2].ToString().Trim();                   
                    string strExcel = "Select   *   From   [" + tableName + "]";
                   
                    System.Data.DataTable excelDt = new System.Data.DataTable();
                    OleDbDataAdapter da = new OleDbDataAdapter(strExcel, conn);
                    da.Fill(excelDt);
                    conn.Close();
                    MessageBox.Show("excel 导入成功", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    if (excelDt != null)
                    {
                        dataGridView1.DataSource = excelDt;
                    }
导出语句:
            mycon.Open();
            string sql = @"SELECT *  INTO [abcef] IN 'D:\111.xls' 'Excel 8.0;' FROM data ";
            OleDbCommand cmd = new OleDbCommand(sql, mycon);
            cmd.ExecuteNonQuery();
            mycon.Close();可不可以修改一下我的程序
让导入的第四列为两位小数的数值，
让导出的第四列为两位小数的数值，（1994.10不要变成1994.1)

Answer 1

double d=1994.10;
string str1=String.Format("{0:F}",d);
string result= String.Format("{0:N2}",Convert.ToDecimal("").ToString()); 

Answer 2

可以设置数据库里面的数据类型是
DEC(18,2)

Answer 3

//导入
if (excelDt != null) 
                    { 
                        if(excelDt.Rows.Count>0)
                         {
                            for(int i=0;i<excelDt.Rows.Count;i++)
                              {
                                 execlDt.Rows[i][3]=execlDt.Rows[i][3].ToString("F2");
                         }
                        dataGridView1.DataSource = excelDt; 
                    } 
//导出
string sql = @"SELECT *,Convert(decimal(18,2),Number) INTO [abcef] IN 'D:\111.xls' 'Excel 8.0;' FROM data "; 
//Number为你第四列在数据表里的字段名