SelectListItem selected = true not working in view

Method to get genders with select:

private Dictionary<string,string> GetGender(){
    Dictionary<string, string> myDic = new Dictionary<string, string>();
    myDic.Add(System.DBNull.Value.ToString(), "Select");
    myDic.Add("Male", "Male");
    myDic.Add("Female", "Female");
    return myDic;
}

In the controller:

//without selectedValue
ViewData["gender"]  = new SelectList(GetGender(), "Key", "Value");

OR

//"Male" as selectedValue
ViewData["gender"]  = new SelectList(GetGender(), "Key", "Value", "Male");

In the view:

Html.DropDownListFor(m => m.Gender, (SelectList)(ViewData["gender"]),
                        new { @class = "span2" })

This is a known bug in ASP.NET MVC Razor View. As per the known bug documentation

"The reason behind this problem is that asp.net MVC first looks for a match between the name of the drop down and property on the model. If there’s a match, the selected value of the SelectList is overridden. Changing the name of the drop down is all it takes to remedy the issue."

I'm here giving a small example which you can use to test the resolution.

 var paymentTypeList = new List<SelectListItem>
                {
                    new SelectListItem { Text = "Select Payment Type", Value = "NA" },
                    new SelectListItem { Text = "Card", Value = "Card" },
                    new SelectListItem { Text = "Paytm Wallet", Value = "Paytm Wallet" },
                    new SelectListItem { Text = "Cash", Value = "Cash", Selected = true },
                    new SelectListItem { Text = "Credit", Value = "Credit" },
                    new SelectListItem { Text = "Other", Value = "Other" }
                };
 ViewBag.paymentTypeList = paymentTypeList;

Resolution Option 1 (Easiest) - Change the Name of declaration id of select list id in MVC view e.g

@Html.DropDownList("paymentTypeListNew", (List<SelectListItem>)ViewBag.paymentTypeList, new { @class = "form-control select2 select1" })

Resolution 2: (Use only single constructor of @Html.DropDownList that matches viewbag/viewdata property)

To ensure that selected item (cash in this example) gets selected do the following in MVC Razor View. Use only the following constructor without any CSS or new object values

 @Html.DropDownList("paymentTypeList") 

Now if you are worried that you cannot initialize the CSS then you need to initialize the css programitally. For example if you are using Jquery then can you can use

$("#paymentTypeList").addClass("form-control");
            $("#paymentTypeList").addClass("select2");

I suggest it's better if you use strongly typed property for SelectList (rather than using ViewBag/ViewData). I believe what you are expecting is that your dropdownlist to be pre-selected with the gender selection made in the model. Here is a solution (code is not 100% clean. But this will work)

Model

public class TestModel
{
    public string Gender { get; set; }

    public IEnumerable<SelectListItem> GenderList
    {
        get
        {
            List<SelectListItem> list = new List<SelectListItem> { new SelectListItem() { Text = "Select", Value = "Select" }, new SelectListItem() { Text = "Male", Value = "Male" }, new SelectListItem() { Text = "Female", Value = "Female" } };
            return list.Select(l => new SelectListItem { Selected = (l.Value == Gender), Text = l.Text, Value = l.Value });
        }
    }
}

Controller Action

public ActionResult MyView()
{
    TestModel m = new TestModel();
    m.Gender = "Female";
    return View(m);
}

MyView.cshtml

@model TestModel

@{
    ViewBag.Title = "MyView";
}

<h2>MyView</h2>
@using (Html.BeginForm())
{
    <div>
          @Html.DropDownListFor(model => model.Gender, Model.GenderList)
    </div>
}

OUTPUT

dropdown with 'Female' option selected

EDIT

Based on comments find below links to sample projects

1) https://github.com/prashanth-t/DropdownDemo_BareBones (Using the MVC 4 empty template. Smaller file size with bare minimum)

2) https://github.com/prashanth-t/DropdownDemo (Using the MVC 4 internet application template. Bigger file size)

Try this instead in the controller:

string[] gender = new string[] {"Male", "Female"};
string selectedGender = gender.Where(x => x.StartsWith(pm.gender)).FirstOrDefault();
ViewData["gender"] = new SelectList(gender, selectedGender);

And in the view:

<%: Html.Dropdownlist(x => x.Gender, ViewData["gender"], "Select") %>