Add or delete User roles from Web.Config file programmatically using C# in ASP.Net

http://aspsnippets.com/Articles/Implement-Role-based-security-Page-access-and-ShowHide-Menu-items-based-on-Role-in-ASPNet.aspx

Please download the Sample from the above link.

Please refer this code to add Or Delete Roles.

HTML

<h1>
    Home</h1>
<br />
<asp:DropDownList ID="ddlRoleTypes" runat="server">
    <asp:ListItem Text="Allow" />
    <asp:ListItem Text="Deny" />
</asp:DropDownList>
<br />
Roles
<asp:TextBox ID="txtRoles" runat="server" />
<br />
Add Roles
<br />
<asp:Button ID="btnAddRoles" runat="server" Text="Add Roles" OnClick="AddRoles" />
<br />
Delete Role by name
<br />
<asp:TextBox ID="txtDeleteRoles" runat="server" />
<br />
<asp:Button Text="Delete Role" ID="btnDeleteRoles" OnClick="DeleteRole" runat="server" />

Namespace

using System.Web.Security;
using System.Xml;
using System.Web.Configuration;

C#

protected void AddRoles(object sender, EventArgs e)
    {
        string path = Server.MapPath("~/Web.Config");
        XmlDocument xDoc = new XmlDocument();
        xDoc.Load(path);
        XmlNodeList list = xDoc.DocumentElement.SelectNodes("system.web/authorization");
        if (list.Count > 0)
        {
            XmlElement newAllowelement = xDoc.CreateElement("allow");
            XmlAttribute newAllowAttrib = xDoc.CreateAttribute("roles");
            AuthorizationRule newRule;
            if (this.ddlRoleTypes.SelectedItem.Value == "Allow")
            {
                newRule = new AuthorizationRule(AuthorizationRuleAction.Allow);
            }

            else
            {
                newRule = new AuthorizationRule(AuthorizationRuleAction.Deny);
            }
            newRule.Roles.Add(ddlRoleTypes.SelectedItem.Value).ToString();
            newAllowAttrib.Value = this.txtRoles.Text.Trim();
            newAllowelement.Attributes.Append(newAllowAttrib);
            list[0].AppendChild(newAllowelement);

            xDoc.PreserveWhitespace = true;
            //write to web.config file using xml writer
            XmlTextWriter xwriter = new XmlTextWriter(path, null);
            xDoc.WriteTo(xwriter);
            xwriter.Close();
        }
        else
        {
            ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Please add authorization under system.web Node in Web config file')", true);
        }
    }

    protected void DeleteRole(object sender, EventArgs e)
    {
        string path = Server.MapPath("~/Web.Config");
        XmlDocument xDoc = new XmlDocument();
        xDoc.Load(path);
        XmlNodeList list = xDoc.DocumentElement.SelectNodes("system.web/authorization");
        if (list.Count > 0)
        {
            for (int i = 0; i < list[0].ChildNodes.Count; i++)
            {
                if (list[0].ChildNodes[i].Name == "allow")
                {
                    if (list[0].ChildNodes[i].Attributes["roles"].Value == txtDeleteRoles.Text)
                    {
                        list[0].ChildNodes[i].ParentNode.RemoveChild(list[0].ChildNodes[i]);
                        xDoc.PreserveWhitespace = true;
                        XmlTextWriter xwriter = new XmlTextWriter(path, null);
                        xDoc.WriteTo(xwriter);
                        xwriter.Close();
                    }
                }
            }

        }
        else
        {
            ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('No Role found!')", true);
        }
    }
}