Question

我有这段代码将它从Form1发送到Form2：

public partial class Form1 : Form
{
    public ShoppingBasket myBasket = new ShoppingBasket();

    public Form1()
    {
        InitializeComponent();
    }

    private void editButton_Click(object sender, EventArgs e)
    {
        int c = lstCart.Items.Count - 1;

        for (int i = c; i <= 0; i++)
        {
            if (lstCart.GetSelected(i))
            {
                Form2 fm2 = new Form2();
                fm2.productNameTextBox.Text = myBasket[i].ProductName;
                fm2.quantityTextBox.Text = Convert.ToString(myBasket[i].Quantity);
                fm2.latestPriceTextBox.Text = Convert.ToString(myBasket[i].LatestPrice);
                fm2.ShowDialog();
            }
        }
    }
}

然后这是我的Form2代码：

public partial class Form2 : Form
{
    public Form2()
    {
        InitializeComponent();
    }
    Form1 fm1 = new Form1();

    private void okBtn_Click(object sender, EventArgs e)
    {
        int c = fm1.lstCart.Items.Count - 1;

        for (int i = c; i <= 0; i++)
        {
            if (this.fm1.lstCart.GetSelected(i))
            {
                this.fm1.myBasket[i].ProductName = this.productNameTextBox.Text;
                this.fm1.myBasket[i].Quantity = Convert.ToInt32(this.quantityTextBox.Text);
                this.fm1.myBasket[i].LatestPrice = Convert.ToDecimal(this.latestPriceTextBox.Text);
                this.Close();
            }
        }
    }

    private void cancelBtn_Click(object sender, EventArgs e)
    {
        this.Close();
    }
}

这是我的ShoppingBasket类：

public class ShoppingBasket : List<OrderItem>
{
    public ShoppingBasket()
    {

    }

    public decimal BasketTotal { get; set; }

    public new void Add(OrderItem i)
    {
        base.Add(i);
    }

    public new void Remove(OrderItem i)
    {
        base.Remove(i);
    }

OrderItem类：

public class OrderItem
{
    public OrderItem(string productName, 
    decimal latestPrice, int quantity)
    {
        ProductName = productName;
        LatestPrice = latestPrice;
        Quantity = quantity;
        TotalOrder = latestPrice * quantity;
    }

    public string ProductName { get; set; }

    public decimal LatestPrice { get; set; }

    public int Quantity { get; set; }

    public decimal TotalOrder { get; set; }
}

我得到的问题是它给了我：'ArgumentOutOfRangeException未处理'说“索引-1超出范围。参数名称：索引”指向这一行： if（this.fm1.lstCart.GetSelected（i））

但之前它给了我另一个错误，说“对象引用未设置为对象的实例。”

如何将以前在Form1中所选字段中的值更改为从Form2传递回Form1的值？

Answer 1

正如daniel所说，你需要将对form1的引用传递给form2，我个人会在构造函数中执行它

public Form2(Form1 form)
{
    fm1 = form;
}

然后你真的应该尝试只在可能的情况下更新表单中的表单字段，因为form2是模态的我会做类似的事情

using(Form2 fm2 = new Form2(this))
{
    fm2.productNameTextBox.Text = myBasket[i].ProductName;
    fm2.quantityTextBox.Text = Convert.ToString(myBasket[i].Quantity);
    fm2.latestPriceTextBox.Text = Convert.ToString(myBasket[i].LatestPrice);
    if(DialogResult.OK == fm2.ShowDialog(this))
    {
        myBasket[i].ProductName = frm2.productNameTextBox.Text;
        myBasket[i].Quantity = Convert.ToInt32(frm2.quantityTextBox.Text);
        myBasket[i].LatestPrice = Convert.ToDecimal(frm2.latestPriceTextBox.Text);
    }
}

然后关闭form2使用

this.DialogResult = DialogResult.OK;

Answer 2

当您在new Form1()中创建Form2时，您正在创建一个没有填充数据的全新Form1。它不是原始Form1调用Form2。

所以，你需要的是将Form1设置为原始版本，而不是新版本：

public partial class Form2 : Form
{
    public Form2()
    {
        InitializeComponent();
    }

    public Form1 fm1; //just declare, but let Form1 do the assign job.

    //the rest of the code...
}

表格1

for (int i = c; i <= 0; i++)
{
    if (lstCart.GetSelected(i))
    {
        Form2 fm2 = new Form2();
        fm2.productNameTextBox.Text = myBasket[i].ProductName;
        fm2.quantityTextBox.Text = Convert.ToString(myBasket[i].Quantity);
        fm2.latestPriceTextBox.Text = Convert.ToString(myBasket[i].LatestPrice);

        //here is the news:
        fm2.fm1 = this;

        fm2.ShowDialog();
    }
}

我知道如何从Form1发送信息到Form2，但如果数据包含在Form1中的List <t>中，如何编辑并发送回来？</t>

2 个答案: