如何在用户控件的 onchange 事件中保留文本框的先前值

Question

我有一个带有几个文本框的用户控件，如果在 OnTextChanged 事件中不满足 txtA、txtB、txtC 文本框总和的条件，我如何保留文本框 txtOne 的先前值。

变量"one"被认为是文本框的前一个值。我在用户控件中添加了以下代码。

protected void txtOne_TextChanged(object sender, EventArgs e)
{
    total = Convert.ToInt32(txtA.Text) + Convert.ToInt32(txtB.Text) + Convert.ToInt32(txtC.Text);
    if (total > Convert.ToInt32(txtOne.Text.ToString()))
    {
         txtOne.Text = one.ToString();
    }
}

这里 "one" 变量的值为 0。它应该存储以前的值。你能给我一个关于将值存储在 "one" 变量中的位置的线索吗？

Answer 1

下面的代码没有以任何方式优化或推广。它尽可能接近您的示例代码，旨在根据您的原始代码向您展示答案。我建议使用组合框而不是文本框，and/or 使用验证来确保条目都是数字。下面的代码不会走那么远 - 它只会根据您提供的代码回答您的问题：

TextBox txtA = new TextBox();
    TextBox txtB = new TextBox();
    TextBox txtC = new TextBox();
    int total = 0;
    TextBox txtOne = new TextBox();
    string newOne = "";
    string someDefaultValue = "";
    string lastOne = "";
    if(txtA.Text.Length==0||txtB.Text.Length==0||txtC.Text.Length==0){
        //user has not entered required fields -- abort
        return;
    }
    bool isTextChanging = true;//CHANGE TO FALSE AT END OF PAGE_ONLOAD
    protected void txtOne_TextChanged(object sender, EventArgs e)
    {
        if(!isTextChanging){
        isTextChanging=true;
        total = getTotal(new string[] { txtA.Text, txtB.Text, txtC.Text });
        if (total > -1)
        {
            int totalTest = 0;
            if (int.TryParse(txtOne.Text, out totalTest))
            {
                if (total > totalTest)
                {
                    txtOne.Text = lastOne.Length > 0 ? lastOne : someDefaultValue;//default value for the first run when there is no last value 
                    lastOne = newOne;//whatever the value of "one" is this time
                }
            }
            else
            {
                MessageBox.Show("YOu must only enter numbers");
            }
        }
        }
        isTextChanging=false;
    }
    private int getTotal(string[] inputs)
    {
        int total = 0;
        int subTotal = 0;
        foreach(string input in inputs)
        {
            if(int.TryParse(input,out subTotal)){
                total += subTotal;
            }else{
                MessageBox.Show("You must only enter numbers");
                return -1;
            }
        }
        return total;
    }

Answer 2

好的 - 我很困惑。可能是语言的问题。这就是您要实现的目标，但使用的是文本框而不是下拉列表吗？

前端：

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="SO_Web.WebForm1" %>

<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div id="div_Boxes" runat="server">

</div>
</form>
</body>
</html>

后端：

protected void Page_Load(object sender, EventArgs e)
    {
        createBoxes();
    }
    string[] boxNames = { "One", "Two", "Three" };
    private void createBoxes()
    {

        int x = 0;
        int y = 10;
        Panel p = new Panel();
        foreach (string name in boxNames)
        {

            Label l = new Label();
            l.ID = "lbl_" + name;
            l.Text = "Select Value " + name;
            l.Style.Add("float", "left");
            DropDownList c = new DropDownList();
            c.ID = "cbx_" + name;
            c.Items.Add("Select One");
            for (int i = 1; i < 101; i++)
            {
                c.Items.Add(i.ToString());
            }
            c.SelectedIndex = 0;
            c.AutoPostBack = true;
            c.Style.Add("display", "block");
            c.SelectedIndexChanged += cbx_Changed;
            p.Controls.Add(l);
            p.Controls.Add(c);
        }

        Label lbl_Total = new Label();
        lbl_Total.Text = "Your Total:";
        TextBox txt_Total = new TextBox();
        txt_Total.ID = "txt_Total";
        txt_Total.Width = 75;
        p.Controls.Add(lbl_Total);
        p.Controls.Add(txt_Total);
        p.Width = 300;
        p.Height = 200;
        div_Boxes.Controls.Add(p);
    }
    protected void cbx_Changed(object sender, EventArgs e)
    {
        bool proceed = true;
        int total = 0;
        foreach (string name in boxNames)
        {
            DropDownList c = (DropDownList)findControl(this.Page.Controls,"cbx_" + name);
            if (c.SelectedIndex == 0)
            {
                proceed = false;
            }
            else
            {
                total += c.SelectedIndex;

            }
        }
        if (proceed)
        {
            ((TextBox)findControl(this.Page.Controls,"txt_Total")).Text = total.ToString("C2");
        }

    }
    private Control findControl(ControlCollection page, string id)
    {
        foreach (Control c in page)
        {
            if (c.ID == id)
            {
                return c;
            }

            if (c.HasControls())
            {
                var res = findControl(c.Controls, id);

                if (res != null)
                {
                    return res;
                }
            }
        }
        return null;
    }

但是您想使用文本框并允许用户键入条目，并且您希望最大值为 110。如果用户为所有三个框输入的值均小于 110，则您需要总计。如果用户在任何框中输入 >110，您希望值重置为 100？对吗？

如何在用户控件的 onchange 事件中保留文本框的先前值

How to retain previous value for a textbox in onchange event in usercontrol

c#

asp.net

user-controls