c# - How to remove an item from Dictionary

Dictionary Remove() Method

.Net framework dictionary Remove() method allow us to remove the value with the specified key from the Dictionary<TKey, TValue>. this Dictionary<TKey, TValue>.Remove() method exists under System.Collections.Generic namespace. this method require to pass a parameter named 'key'.

the 'key' parameter value type is 'TKey' which represents the key of the element to remove. the Remove() method retrun value data type is System.Boolean. this method return 'true', if the element is successfully found and removed; otherwise this method return 'false'. this method also return 'false', if 'key' is not found in dictionary.

the Remove() method implements as IDictionary<TKey, TValue>.Remove(TKey). this method throw ArgumentNullException exception, if the 'key' is null. if the specified 'key' is not found in dictionary then the dictionary remain unchanged and no exception is thrown.

the following asp.net c# example code demonstrate us how can we remove dictionary element by key programmatically at run time in an asp.net application.

DictionaryRemoveMethod.aspx


<%@ Page Language="C#" AutoEventWireup="true" %>
<%@ Import Namespace="System.Collections.Generic" %>

<!DOCTYPE html>
<script runat="server">
    protected void Button1_Click(object sender, System.EventArgs e)
    {
        Dictionary<string, string> colors = new Dictionary<string, string>();
        colors.Add("PaleVioletRed", "#D87093");
        colors.Add("PaleGreen", "#98FB98");
        colors.Add("Purple", "#800080");
        colors.Add("SteelBlue", "#4682B4");

        Label1.Text = "Dictionary Keys...<br />";

        foreach (string color in colors.Keys)
        {
            Label1.Text += color + "<br />";
        }

        //Remove() method remove the value with the specified key from the Dictionary.
        colors.Remove("Purple");

        Label1.Text += "<br />After Call Remove() Method With Key 'Purple'. Dictionary Keys...<br />";
        foreach (string color in colors.Keys)
        {
            Label1.Text += color + "<br />";
        }

    }
</script>

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>Dictionary Remove() Method - How to remove the value with the specified key from Dictionary</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <h2 style="color:Navy; font-style:italic;">
            System.Collections.Generic.Dictionary Remove() Method
            <br /> How to remove the value with the specified key from Dictionary
        </h2>
        <hr width="600" align="left" color="Navy" />
        <br />
        <asp:Label
             ID="Label1"
             runat="server"
             ForeColor="Purple"
             Font-Names="Courier New"
             Font-Size="Large"
             >
        </asp:Label>
        <br />
        <asp:Button 
            ID="Button1"
            runat="server"
            OnClick="Button1_Click"
            Text="Test Dictionary Remove() Method"
            Height="45"
            Font-Bold="true"
            ForeColor="DodgerBlue"
            />
    </div>
    </form>
</body>
</html>

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