How can i use FindControl method in asp.net?

问题:

How can i use findControl and how can i get id's according to FindControl method? i need to get all TextBox data there are 40 textbox. And TextBoxid data...

i reall want to learn also linq method ;)

  protected void Button1_Click(object sender, EventArgs e)
        {
          //  SetRecursiveTextBoxAndLabels(PlaceHolder1);
            CreateForm creater = new CreateForm();
            creater.Holder = PlaceHolder1;
            creater.SetAccessForm();

            if (PlaceHolder1.Controls.Count > 0)
            {
                foreach (Control item in PlaceHolder1.Controls)
                {
                    item.FindControl(item.ID) is TextBox-------> How can i control is textBox?  Because there are labels grid.... 
                }
            }

        }

i need only this :

    ENG_ACCESS engAccess = new ENG_ACCESS();
            Type engTyp = engAccess.GetType();
            PropertyInfo[] properties = engTyp.GetProperties();

            TextBox txtbox = new TextBox();

            foreach (PropertyInfo strColumn in properties)
              {
                  txtbox = (TextBox)Page.FindControl("txt" + strColumn.Name);
                ListBox1.Items.Add(txtbox.Text);
            }

My WHOLE CODES:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Reflection;

namespace RecursiveAddTextBox
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            using (var dataCtx = new DataClasses1DataContext())
            {

                if (!IsPostBack)
                {
                    SetRecursiveTextBoxAndLabels();
                }



            }

        }

        void SetRecursiveTextBoxAndLabels()
        {
            TextBox txtBox;
            Label lbl;

                ENG_ACCESS eng = new ENG_ACCESS();
                Type typ = eng.GetType();
                PropertyInfo[] properties = typ.GetProperties();
                PlaceHolder1.Controls.Add(new LiteralControl("<table>"));
                for( int i =0;  i<properties.Length; i++)
                {
                    lbl = new Label();
                    lbl.ID = "lbl" + properties[i].Name;
                    lbl.Text = properties[i].Name;
                    PlaceHolder1.Controls.Add(new LiteralControl("<tr><td>"));
                    PlaceHolder1.Controls.Add(lbl);
                    PlaceHolder1.Controls.Add(new LiteralControl("</td><td>"));
                    txtBox = new TextBox();
                    txtBox.ID ="txt"+properties[i].Name;
                    PlaceHolder1.Controls.Add(txtBox);
                    PlaceHolder1.Controls.Add(new LiteralControl("</td></tr>"));
                }
                PlaceHolder1.Controls.Add(new LiteralControl("</table>"));

        }

        protected void Button1_Click(object sender, EventArgs e)
        {
           SetRecursiveTextBoxAndLabels();



        }
        protected void Button2_Click(object sender, EventArgs e)
        {

            if (PlaceHolder1.Controls.Count > 0)
            {
                foreach (Control item in PlaceHolder1.Controls)
                {
                    if (item is TextBox)
                    {
                        TextBox t1 = (TextBox)PlaceHolder1.FindControl(item.ID);
                    }
                }
            }

        }

    }

回答1:

protected void Button1_Click(object sender, EventArgs e) 
        { 
          //  SetRecursiveTextBoxAndLabels(PlaceHolder1); 
            CreateForm creater = new CreateForm(); 
            creater.Holder = PlaceHolder1; 
            creater.SetAccessForm(); 

            if (PlaceHolder1.Controls.Count > 0) 
            { 
                foreach (Control item in PlaceHolder1.Controls) 
                { 
                     if (item is TextBox)
                         TextBox t1=(TextBox)PlaceHolder1.FindControl(item.ID);
                } 
            } 
        }

回答2:

As an extension to the answer provided by Pranay, I think you are probably falling foul of INamingContainer.

The asp.net control ID's are created using nested controlnames. Take a look at MSDN for more information on webcontrols and the INamingContainer interface

回答3:

Why are you looping through each control and then asking the page to find the control you already have?

In other words, if (item is TextBox) then item is the TextBox you are looking for!

Remember that FindControl is not recursive so you have to call FindControl on the instance of the naming container that actually contains the control you want to find.

回答4:

Add this extension method:

    /// <summary>
    /// Finds all controls with the given type anywhere under the root
    /// </summary>
    public static IList<Control> FindControlsRecursive<FindType>( this ControlCollection root )
    {
        Type toFind = typeof( FindType );
        List<Control> controls = new List<Control>();
        if ( root != null && root.Count > 0 )
        {
            foreach ( Control control in root )
            {
                if ( control != null && ( toFind.IsAssignableFrom( control.GetType() ) ) )
                {
                    controls.Add( control );
                }
                if ( control != null )
                {
                    controls.AddRange( control.Controls.FindControlsRecursive<FindType>() );
                }
            }
        }
        return controls;
    }

then call it with:

var textBoxes = Page.Controls.FindControlsRecursive<TextBox>();
foreach(var tb in textBoxes)
{
    tb.Text = "";
}