c# - How to find duplicate values from a Dictionary

Dictionary find duplicate values
dictionary-find-duplicate-values.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,"Golden Pheasant"},  
            {2,"Southern Screamer"},  
            {3,"Golden Pheasant"},  
            {4,"Swan Goose"},  
            {5,"Swan Goose"},  
            {6,"Golden Pheasant"},  
            {7,"Greylag Goose"}  
        };

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

        //get dictionary duplicate values.
        var duplicatesValue = birds.GroupBy(x => x.Value).Where(x => x.Count() > 1);

        Label1.Text += "<br /><br />dictionary duplicate values..........<br />";  
        foreach(var item in duplicatesValue)
        {
            Label1.Text += item.Key + "<br />";
        }
    }      
</script>      
      
<html xmlns="http://www.w3.org/1999/xhtml">      
<head id="Head1" runat="server">      
    <title>c# example - dictionary find duplicate values</title>      
</head>      
<body>      
    <form id="form1" runat="server">      
    <div>      
        <h2 style="color:MidnightBlue; font-style:italic;">      
            c# example - dictionary find duplicate values
        </h2>      
        <hr width="550" align="left" color="Gainsboro" />      
        <asp:Label       
            ID="Label1"       
            runat="server"      
            Font-Size="Large"    
            >      
        </asp:Label>      
        <br /><br />    
        <asp:Button       
            ID="Button1"       
            runat="server"       
            Text="dictionary find duplicate values"      
            OnClick="Button1_Click"    
            Height="40"      
            Font-Bold="true"      
            />      
    </div>      
    </form>      
</body>      
</html>
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