Question

我正在创建一个简单的项目，我从用户那里获取“id”和“name”并将其存储到Access Data库中。每当我按Store按钮System.NullReferenceException错误就出来了。这是代码

我宣布Oledpconnection。

public OleDbConnection Con; 
    public Form1()
    {
        InitializeComponent();
        string connetionString = null;
        connetionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:/Users/Mujahid/Documents/Visual Studio 2008/Projects/ts/ts/ts.accdb";
        OleDbConnection Con = null;
        Con = new OleDbConnection(connetionString);

        try
        {
            Con.Open();
            MessageBox.Show("Connection Open ! ");
            Con.Close();

        }
        catch (Exception)
        {
            MessageBox.Show("Can not open connection ! ");
        }

    }

这是插入按钮编程

OleDbCommand cmd = new OleDbCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText="insert into ts(ID,Name)" +"Values ('"+textBox1.Text+"','"+textBox2.Text+"')" ; 
        cmd.Connection= Con;
        Con.Open();
        cmd.ExecuteNonQuery();
        Con.Close();

请帮助!!

Answer 1

Con需要是表单范围对象，而不是表单构造函数中的重新声明。

public OleDbConnection Con;  
public Form1() 
{ 
    InitializeComponent(); 
    string connetionString = null; 
    connetionString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:/Users/Mujahid/Documents/Visual Studio 2008/Projects/ts/ts/ts.accdb"; 

    Con = new OleDbConnection(connetionString); 

    try 
    { 
        Con.Open(); 
        MessageBox.Show("Connection Open ! "); 
        Con.Close(); 

    } 
    catch (Exception) 
    { 
        MessageBox.Show("Can not open connection ! "); 
    } 

}

Answer 2

public OleDbConnection Con;

...

OleDbConnection Con = null;

您永远不会初始化类作用域连接实例。

System.NullReferenceException在Access数据库中存储数据时出错

2 个答案: