c# - How to add a key value pair to a Dictionary

Dictionary add key value pair
dictionary-add-key-value-pair.aspx

<%@ Page Language="C#" AutoEventWireup="true"%>

<!DOCTYPE html>  
<script runat="server"> 
    protected void Button1_Click(object sender, System.EventArgs e)  
    {
        Dictionary<int, string> plants = new Dictionary<int, string>();
        plants.Add(1, "Mahogany Birch");
        plants.Add(2, "Silver Birch");
        plants.Add(3, "Spice Birch");

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

        //this line create a new keyvaluepair;
        KeyValuePair<int, string> pair = new KeyValuePair<int, string>(4, "Bay Laurel");
        
        //this line new keyvaluepair to dictionary.
        plants.Add(pair.Key,pair.Value);
        
        Label1.Text += "<br />after adding new key value pair.....<br />";

        foreach (KeyValuePair<int,string> p in  plants)
        {
            Label1.Text += p.Key + " | " + p.Value + "<br />";
        }
    }  
</script>  
  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head id="Head1" runat="server">  
    <title>c# example - dictionary add key value pair</title>  
</head>  
<body>  
    <form id="form1" runat="server">  
    <div>  
        <h2 style="color:MidnightBlue; font-style:italic;">  
            c# example - dictionary add key value pair
        </h2>  
        <hr width="550" align="left" color="Gainsboro" />  
        <asp:Label   
            ID="Label1"   
            runat="server"  
            Font-Size="X-Large"
            >  
        </asp:Label>  
        <br /><br />
        <asp:Button   
            ID="Button1"   
            runat="server"   
            Text="dictionary add key value pair"  
            OnClick="Button1_Click"
            Height="40"  
            Font-Bold="true"  
            />  
    </div>  
    </form>  
</body>  
</html>
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