使用类和存储过程在C#(Visual 2015)中将数据插入SQL Server 2014

Question

我在SQL Server数据库中插入数据时遇到问题.我正在使用一个名为book的类,在我的表单设计中,当我想插入数据时,我收到错误.

class Book
{
    private string _bookname;
    private int _bookcode;
    private int _numberofpages;
    private string _author;
    private string _publicationname;
    private string _genre;
    private int _publishyear;
    private string _language;
     SqlConnection _sqlcon = new SqlConnection();

    public Book(SqlConnection sqlcon)
    {
        _sqlcon = sqlcon;
    }

    public string bookname
    {
        get { return _bookname; }
        set { _bookname = value; }
    }
    public int bookcode
    { 
    get { return _bookcode; }
    set { _bookcode = value; }
        }
    public int numberofpages
    {
        get { return _numberofpages; }
        set { _numberofpages = value; }

    }
    public string author
    {
        get { return _author; }
        set { _author = value; }
    }
    public string publicationname
        {
        get { return _publicationname; }
        set { _publicationname = value; }
        }
    public string genre
    {
        get { return _genre; }
        set { _genre = value; }
    }
    public int publishyear
    {
        get { return _publishyear; }
        set { _publishyear = value; }
    }
    public string language
    {
        get { return _language; }
        set { _language = value; }
    }

    public void SaveBook()
    {
        SqlConnection _sqlcon = new SqlConnection();

        SqlCommand com = new SqlCommand();
        com.CommandType = CommandType.StoredProcedure;
        com.Connection = _sqlcon;
        com.CommandText = "PROC_BOOK1";
        com.Parameters.Add("@nameofbook", SqlDbType.VarChar).Value = bookname;
        com.Parameters.Add("@codeofbook", SqlDbType.Int).Value = bookcode;
        com.Parameters.Add("@npages", SqlDbType.Int).Value = numberofpages;
        com.Parameters.Add("@bookauthor", SqlDbType.VarChar).Value = author;
        com.Parameters.Add("@publicationname", SqlDbType.VarChar).Value = publicationname;
        com.Parameters.Add("@bookgenre", SqlDbType.VarChar).Value = genre;
        com.Parameters.Add("@pyear", SqlDbType.Int).Value = publishyear;
        com.Parameters.Add("@booklanguage", SqlDbType.VarChar).Value = language;

        com.ExecuteNonQuery();

这是我的插入按钮:

public partial class Form1 : Form
{
    private SqlConnection _sqlcon = new SqlConnection();
    private Book _book1;
    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void btnsabt_Click(object sender, EventArgs e)
    {

        _book1 = new Book(_sqlcon);
        _book1.bookname = txtbookname.Text;
        _book1.bookcode = Convert.ToInt32(txtbookcode.Text);
        _book1.numberofpages = Convert.ToInt32(txtnumberofpages.Text);
        _book1.author = txtauthor.Text;
        _book1.publicationname = txtpublication.Text;
        _book1.genre = txtgenre.Text;
        _book1.publishyear = Convert.ToInt32(txtpublishyear.Text);
        _book1.language = txtlanguage.Text;
        _book1.SaveBook();
        MessageBox.Show("saved succesfully");

    }

以下是错误快照:

Answer 1

您的问题与您设计此Book模型的方式有关.

您强制用户使用接收SqlConnection的构造函数然后(这可能只是一个错误)您在SaveBook方法中创建SqlConnection的新实例(没有连接字符串).
您可能希望使用构造函数中传递的SqlConnection,并且您希望此类的客户端使用适当的connectionstring设置对其进行初始化并打开它.

因此,如果您真的希望您的客户端提供连接,那么使用connectionstring初始化它并在click方法中初始化Book实例之前打开它.当然,删除在SaveBook方法中创建新连接的行.

public void SaveBook()
{
    // This line defines a local variable with the same name of the global one
    // It hides the global, if you expect your client to provide the connection
    // then remove the line
    SqlConnection _sqlcon = new SqlConnection();
    ....

我觉得这个设计不太明智.这是一个大黄蜂的巢已经开始以各种可能的方式刺痛你.

模型(Book)不应该关注如何将其保存到最终存储(或从中加载),无论是数据库表,XML文件,远程服务还是将来需要做的任何事情.

相反,处理数据库事务的专用类应该具有从Database表中保存和检索Book数据的所有代码(在本例中)

我会用一个名为BookDB的类来设计它

public class BookDB
{
     public bool Save(Book obj)
     {
          using(SqlConnection con = RepositoryUtility.GetConnection())
          {
              // here code to check and save the object
              ....
          }
     }
     public Book LoadByKey(int bookID)
     {
          using(SqlConnection con = RepositoryUtility.GetConnection())
          {
              Book aBook = new Book();
              // here goes the code to load a book from the db using the primarykey
              ....
              return aBook
          }
     }
     ... other db methods based ....
}