我正在创建一个向Excel写入一些数据的基本程序。我是C＃的新手，当然是EPPlus的新手。我一直很难找到有关此软件包的良好文档，但是。.
我的代码如下。
using System.IO;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using OfficeOpenXml;
using Microsoft.VisualBasic;
/* CHANGELOG
* 11/26/2019
* Added basic support for excel database using EPPlus library
*
*/
/* BUGS, FIXES, AND TODO
*
* ******BUGS******
*
* [] Fix loop to loop through each item in given array instead of specified length. Perhaps a foreach makes more sense?
*
*
*
* ******TODO******
* [x] Figure out best way to write information to a file (Excel?)
* [] Create Duplicate Entry detector?
* [] Possible to loop through args in visitor constructor?
* [] Prefill information from membership info (Bar code on mem card?)
* [] Set tab index of all items
* [] Allow user to export database to excel w/ path of choosing.
* []
*
*
*/
namespace Nonprofit_Attendance_App
{
public partial class Form1 : Form
{
//Declare Global Variables
public static class Globals
{
public static string excelSheet = "";
public static ExcelWorksheet wsSheet1;
public static ExcelPackage ExcelPkg;
public static string userIn;
public static string[] alphabet = { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z" };
public static int dataPosition;
}
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void radioButton2_CheckedChanged(object sender, EventArgs e)
{
}
private void checkBox1_CheckedChanged(object sender, EventArgs e)
{
}
private void checkBox4_CheckedChanged(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
//Create new visitor object with form input
Visitor Paal = new Visitor( vis_zip.Text,
vis_entrance_courtYard.Checked,
vis_entrance_frontDoor.Checked,
vis_reason_general.Checked,
vis_reason_meeting.Checked,
vis_reason_photography.Checked,
vis_reason_cafe.Checked,
vis_firstTime.Checked,
vis_returning.Checked,
vis_both.Checked,
vis_mem.Checked,
vis_mem_lastName.Text );
//Loop through Visitor object to write data to console. DELETE EVENTUALLY
foreach (var item in Paal.vis_data)
{
Console.WriteLine(item);
}
writeData(Paal.vis_data);
//Clear form after submit
vis_zip.Text = string.Empty;
vis_entrance_courtYard.Checked = false;
vis_entrance_frontDoor.Checked = false;
vis_reason_general.Checked = false;
vis_reason_meeting.Checked = false;
vis_reason_photography.Checked = false;
vis_reason_cafe.Checked = false;
vis_firstTime.Checked = false;
vis_returning.Checked = false;
vis_both.Checked = false;
vis_mem.Checked = false;
vis_mem_lastName.Text = string.Empty;
}
private void textBox1_TextChanged(object sender, EventArgs e)
{
}
private void label6_Click(object sender, EventArgs e)
{
}
class Visitor
{
public string[] vis_data = new string[12];
public Visitor(string zipCode, bool entrance_courtYard, bool entrance_frontDoor, bool vis_reason_general, bool vis_reason_meeting, bool vis_reason_photo, bool vis_reason_cafe, bool vis_firstTime, bool vis_Returning, bool vis_both, bool vis_mem, string vis_mem_lastName)
{
//Write to Excel Sheet
//FIX EMPTY ENTRIES
vis_data[0] = zipCode;
if (entrance_courtYard == true)
{
vis_data[1] = "Courtyard";
}
else
{
vis_data[1] = "Front Door";
}
if (vis_reason_general == true)
{
vis_data[2] += "General Visit";
}
else if (vis_reason_meeting == true)
{
vis_data[2] += "Meeting";
}
else if (vis_reason_cafe == true)
{
vis_data[2] += "Cafe";
}
else if (vis_reason_photo == true)
{
vis_data[2] += "Photography";
}
else
{
vis_data[2] = "null";
}
if (vis_firstTime == true)
{
vis_data[3] = "First Time";
}
else if (vis_Returning == true)
{
vis_data[3] = "Returning";
}
else if (vis_both == true)
{
vis_data[3] = "Both";
}
else
{
vis_data[3] = "null";
}
if (vis_mem)
{
vis_data[4] = vis_mem_lastName;
}
else
{
vis_data[4] = "Not a member";
}
vis_data[5] = DateTime.Now.ToString();
}
}
private void vis_frontDoor_CheckedChanged(object sender, EventArgs e)
{
}
//Enable member last name when member checkbox is checked
private void vis_mem_CheckedChanged(object sender, EventArgs e)
{
if (vis_mem.Checked)
{
vis_mem_lastName.Enabled = true;
}
else
{
vis_mem_lastName.Enabled = false;
}
}
private void vis_mem_lastName_TextChanged(object sender, EventArgs e)
{
}
//Generates Excel database
public static void generateExcel()
{
//get user input for database name
//Excel Sheet Generation
Globals.ExcelPkg = new ExcelPackage();
Globals.wsSheet1 = Globals.ExcelPkg.Workbook.Worksheets.Add("Sheet1");
Globals.wsSheet1.Protection.IsProtected = false;
Globals.wsSheet1.Protection.AllowSelectLockedCells = false;
Globals.excelSheet = @"C:\Users\paalw\documents\database.xlsx";
Globals.ExcelPkg.SaveAs(new FileInfo(@"C:\Users\paalw\documents\database.xlsx"));
}
//TO FINISH
public static void setHeaders()
{
using (ExcelRange Rng = Globals.wsSheet1.Cells)
{
for (int i = 0; i < 12; i++)
{
Rng[Globals.alphabet[i] + 1].Value = i;
}
}
}
public void getDataPosition()
{
using (ExcelRange Rng = Globals.wsSheet1.Cells)
{
for (int i = 0; i < 5; i++)
{
if (Convert.ToBoolean(Rng["A" + i].Value) == false)
{
Globals.dataPosition = i;
Console.WriteLine(Globals.dataPosition);
break;
}
}
}
}
public void writeData(string[] x)
{
using (ExcelRange Rng = Globals.wsSheet1.Cells)
{
int i = 0;
int j = Globals.dataPosition;
foreach (var item in x)
{
Rng[Globals.alphabet[i] + j].Value = x[i];
i++;
}
Globals.dataPosition++;
}
}
private void fileToolStripMenuItem_Click(object sender, EventArgs e)
{
}
private void newToolStripMenuItem_Click(object sender, EventArgs e)
{
if (File.Exists(Globals.excelSheet))
{
Globals.excelSheet = @"C:\Users\paalw\documents\database.xlsx";
//NEED TO set FileLocation to existing Sheet
MessageBox.Show("Connected to Databse");
getDataPosition();
}
else
{
generateExcel();
setHeaders();
getDataPosition();
}
}
private void menuStrip1_ItemClicked(object sender, ToolStripItemClickedEventArgs e)
{
}
private void button2_Click(object sender, EventArgs e)
{
Globals.ExcelPkg.Save();
}
}
}
当我运行Globals.ExcelPkg.Save（）;时，无论它在程序中的什么位置或何时运行，我都会不断收到对象引用错误：
对象引用未设置为对象的实例。
我不清楚为什么会这样，因为当我运行generateExcel（）时；方法，应将Globals.ExcelPkg设置为正在创建的当前数据库。就像每当应用程序运行时，它将完全清除该变量一样。任何帮助将不胜感激，因为在上周我一直在为此努力。
答案 0 :(得分：0)
以上代码在System.NullReferenceException的{{1}}处将Object reference not set to an instance of an object和using (ExcelRange Rng = Globals.wsSheet1.Cells)抛出
因为writeData(string[] x)是在wsSheet1类中声明的，但尚未初始化。另外，在保存Excel文件之前，您还必须在Globals中调用setHeaders()和getDataPosition()方法。
使用EPPlus生成excel的简单示例：
generateExcel()**这里，用户是要存储在excel文件中的用户列表，_path是保存excel文件的位置。
链接到教程 https://riptutorial.com/epplus
https://itenium.be/blog/dotnet/create-xlsx-excel-with-epplus-csharp/