How to group the Drop down Item List C#

In my asp.net MVC web application, I created a model like,

[Key]
public int ID {
  get;
  set;
}

[Required]
public string AccountName {
  get;
  set;
}

public string Description {
  get;
  set;
}

public int ? CurrentAccountID {
  get;
  set;
}

So from the controller, I'm binding the data to the ViewBag like,

ViewBag.CurrentAccountID = new SelectList(db.Accounts.Where(x => x.Status == true && x.CompanyID == CompanyID), "ID", "AccountName");

This is a sample of data now stored in the data table.

But in the view, I want to show the list in the dropdown list grouping by,

Income

Bank

Credit Card

Expenses

Office Expenses

Other Expenses

So the method is I want to group and show MainAccountID-wise data in the dropdown list.

Would appreciate it if anyone guide me on how to do it

This is the html view

<div class="col-sm-8"> 
    @Html.DropDownList("CurrentAccountID", null, "--Select Account Type--", htmlAttributes: new { @class = "form-select acctype", @Id = "AccountTypes", @required = true, oninvalid = "this.setCustomValidity('Please Select the Account Type')", oninput = "this.setCustomValidity('')", })

First step is to include a navigation property to the parent account:

public virtual Account ParentAccount { get; set; }

Then include the parent accounts, and group by the parent AccountName:

var accountsGrouped = db.Accounts
    .Include(x => x.ParentAccount) // Include parent accounts
    .Where(x => x.Status == true && x.CompanyID == CompanyID)
    .OrderBy(x => x.ParentAccount.AccountName)
    .GroupBy(x => x.ParentAccount.AccountName) // Group by parent account name
    .ToList();

ViewBag.AccountsGrouped = accountsGrouped;

Then you'll have to manually create the select element and the option and optgroup elements:

<div class="col-sm-8">
    <select id="AccountTypes" name="CurrentAccountID" class="form-select acctype" required oninvalid="this.setCustomValidity('Please Select the Account Type')" oninput="this.setCustomValidity('')">
        <option value="">--Select Account Type--</option>
        @foreach (var group in ViewBag.AccountsGrouped)
        {
            <optgroup label="@group.Key"> <!-- group.Key is the parent AccountName -->
                @foreach (var item in group)
                {
                    <option value="@item.ID">@item.AccountName</option>
                }
            </optgroup>
        }
    </select>
</div>