帮助新接触C#变量的人 [英] Help someone new to C# variables

问题描述

我试图通过按按钮将数据保存到数据库中，但是由于变量的定义位置，这些变量似乎是私有的.我试图移动它们的定义位置，但这似乎还会产生其他错误.

I am trying to save data to a database on a button push, but the variables seem to be private by the nature of where they are defined. I have tried to move where they are defined, but this seems to produce other errors.

给出一个修复程序，为什么要这样修复?

Given a fix, why was it fixed that way?

代码如下.

namespace enable
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            OleDbConnection favouriteConnection = new System.Data.OleDb.OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=\\\\192.168.123.5\\Share\\Matt\\BugTypes.mdb");
            string strSQL = "SELECT CategoryName, Show " + "FROM [Categories] WHERE Show = 'Yes' " + "ORDER BY CategoryName";
            OleDbDataAdapter adapter = new OleDbDataAdapter(strSQL, favouriteConnection);
            OleDbCommandBuilder cBuilder = new OleDbCommandBuilder(adapter);
            DataTable dTable = new DataTable();
            adapter.Fill(dTable);
            BindingSource bSource = new BindingSource();
            bSource.DataSource = dTable;
            dataGridView1.DataSource = bSource;
            adapter.Update(dTable);
        }
        private void button1_Click(object sender, EventArgs e)
        {
            adapter.Update(dTable);//this is the button that needs to do the save, but can't see the variables.
        }
    }
}

推荐答案

您在构造函数中声明了 dTable 和 adapter ，因此它很快就超出了范围构造函数完成后.

You're declaring dTable and adapter in the constructor, so it goes out of scope as soon as the constructor is completed.

您要将变量声明移到主类中，例如:

You want to move the variable declarations out into the main class, like:

public partial class Form1 : Form
{
    private DataTable dTable;
    private OleDbDataAdapter adapter;

    Public Form1()
    {
         ... your setup here ...
         dTable = new DataTable();
         ... etc ...
    }
}

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