c# - How to remove items from a Dictionary in loop

Dictionary remove in for loop
dictionary-remove-in-loop.aspx

<%@ Page Language="C#" AutoEventWireup="true"%>
  
<!DOCTYPE html>    
<script runat="server">  
    protected void Button1_Click(object sender, System.EventArgs e)
    {
        //initialize a dictionary with keys and values.
        Dictionary<int, string> birds = new Dictionary<int, string>() {
            {1,"Topknot Pigeon"},
            {2,"Mourning Dove"},
            {3,"Kakapo"},
            {4,"Rainbow Lorikeet"},
            {5,"Varied Lorikeet"}
        };

        Label1.Text = "dictionary keys and values..........";
        foreach (KeyValuePair<int , string> pair in birds)
        {
            Label1.Text += "<br />" + pair.Key + " ........ " + pair.Value;
        }

        //create an int array with dictionary keys which are >=3.
        int[] keys = birds.Keys.Where(x => x>=3).ToArray();

        Label1.Text += "<br /><br />removing keys from dictionary which key>=3<br />";

        for (int i = 0; i < keys.Count(); i++)
        {
            //remove element from dictionary.
            birds.Remove(keys[i]);
            Label1.Text += "key [" + keys[i] + "] removed from dictionary<br />";
        
        }

        Label1.Text += "<br />dictionary keys and values after removing elements..........";
        foreach (KeyValuePair<int, string> pair in birds)
        {
            Label1.Text += "<br />" + pair.Key + " ........ " + pair.Value;
        }
    }    
</script>    
    
<html xmlns="http://www.w3.org/1999/xhtml">    
<head id="Head1" runat="server">    
    <title>c# example - dictionary remove in loop</title>    
</head>    
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    <div>    
        <h2 style="color:MidnightBlue; font-style:italic;">    
            c# example - dictionary remove in loop
        </h2>    
        <hr width="550" align="left" color="Gainsboro" />    
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            ID="Label1"     
            runat="server"    
            Font-Size="Large"  
            >    
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        <asp:Button     
            ID="Button1"     
            runat="server"     
            Text="dictionary remove in loop"    
            OnClick="Button1_Click"  
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