Question

我有几种形式，其中一些形式依赖于每种形式之间的信息。在这种情况下，Form 2（AKA testSelect）中所选选项的所选索引是确定Form 3（AKA testPresent）中将发生什么的关键。这被放入一个名为index的整数中。关闭form 2后，index的值肯定是列表框的selectedindex。

然而，在form 3打开并应用它时，它一直重置为0，我无法弄清楚原因。以下是在index中使用/确定form 2的代码以及在form 3中调用它的代码。此外，它是在form 2;

开头定义的public int

     private void lstExams_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {
            //Create a connection object to the DB via string location
            con = new OleDbConnection(connectionString);
            //Open the connection to the DB
            con.Open();

            String sql = "SELECT typeID, description FROM TestConfiguration WHERE examID = " +(lstExams.SelectedIndex +1);
            OleDbDataAdapter da = new OleDbDataAdapter(sql, con);
            //DataSet ds = new DataSet();
            DataTable testConfig = new DataTable();
            //Set the SQL command text

            da.Fill(testConfig);
            lstTestType.DisplayMember = "description";
            lstTestType.ValueMember = "typeID";

            lstTestType.DataSource = testConfig;

            index = lstExams.SelectedIndex + 1;

            MessageBox.Show("INDEX = " + index);

        }
        catch (Exception err)
        {
            //If cannot connect to DB, display the error;
            MessageBox.Show("A Database error has occurred: " + Environment.NewLine + err.Message);
        }
    }

    private void btnStart_Click(object sender, EventArgs e)
    {

        //var testPresent = new testPresent(this);

        testPresent testForm = new testPresent();
        testForm.Show();


        //testForm.difficulty = lstTestType.ValueMember;
        this.Close();

        MessageBox.Show("INDEX IS " + index);
        testForm.eID = (index);


    }

适用于form 3

    public partial class testPresent : Form
{
    public int eID = 0;
    public String difficulty;
    testSelect select = new testSelect();


    //Get the connection path to the DB from the static class
    String connectionString = staticConnectionString.connectionString;
    //Declare connection object
    OleDbConnection con;

    public testPresent()
    {
        InitializeComponent();
    }


    public void testPresent_Load(object sender, EventArgs e)
    {
        try
        {

            int qID;
            Random random = new Random();
            int examID;
            bool valid = false;
            String theQuestion;

            eID += select.index;

            //Create a connection object to the DB via string location
            con = new OleDbConnection(connectionString);
            //Open the connection to the DB
            con.Open();

            MessageBox.Show("eID = " + select.index);

            if (eID == 1)
            {
                ...

            } 

            if (eID == 2)
            {
                ...

            } 

            if (eID == 3)
            {
                ...

            }



        }
        catch (Exception err)
        {
            //If cannot connect to DB, display the error;
            MessageBox.Show("A Database error has occurred: " + Environment.NewLine + err.Message);
        }
    }

哦，是的，这也使用Microsoft Access数据库来填充列表框。

Answer 1

您可以设置值：

testForm.eID = (index);

但是在表单加载后

testPresent_Load

如果完全需要testPresent testForm = new testPresent(); testForm.Show(); // this is where it uses the value // ... testForm.eID = (index); // this is where you set it表单的值，并且它需要立即使用该值，请尝试在构造函数中包含该值：

testPresent

然后，当您创建表单的实例时，您必须将该值传递给它：

public testPresent(int eid) { InitializeComponent(); eID = eid; }

此时不需要在外部设置值，因此它应该是私有的。（无论如何，数据成员应该是对象的私有。）：

testPresent testForm = new testPresent(index); testForm.Show();

C＃为什么我的变量在表单之间没有正确执行？

1 个答案: