CODEWITHSUNDEEP
c#asp.netasp.net-mvcmodel-view-controllerasp.net-mvc-5
IrishChieftain
IrishChieftain

Reputation: 15253

Binding DropDownList from Database

I'm building a view which will display tabular data based on selections from two dropdownlists, the first which selects departments is populated from the database. The second is a static dropdownlist for "Year" which I haven't got to yet. There are answers to similar questions, but I've looked at them and tried everything. I've got to the point where I'm getting a null exception in the view where I created the markup for the dropdownlist.

View:

Departments is coming back as null. I'm new to MVC and pieced this together from online examples. I'm guessing my model is wrong.

@model IEnumerable<BudgetDemo.Models.BudgetsActualsViewModel>

@foreach (var item in Model)
{
    @Html.DropDownListFor(m => item.Departments, 
        new SelectList(item.Departments.Select(x => x.Text)))
}

ViewModel:

public class BudgetsActualsViewModel
{
    [Display(Name = "Cost Center/Department")]
    [Required(ErrorMessage = "Cost Center/Department is required.")]
    [StringLength(62)]
    public string SelectedDepartment { get; set; }
    public IEnumerable<SelectListItem> Departments { get; set; }
}

Controller:

public ActionResult GetBudgetsActuals()   
{
    repo = new BudgetDemoRepository();
    ModelState.Clear();
    return View(repo.GetBudgetsActuals());
}

Repository Class:

public List<BudgetsActualsViewModel> GetBudgetsActuals()  
{
    ...
    List<BudgetsActualsViewModel> budgetsActualsList = new List<BudgetsActualsViewModel>();
    // Query returning correct data from DB here

    for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
    {
        budgetsActualsList.Add(
            new BudgetsActualsViewModel
             {
                 SelectedDepartment = ds.Tables[0].Rows[i]["Department"].ToString()
             }
        );
    }
    return budgetsActualsList;
}

Upvotes: 0

Views: 87

Answers (1)

Jamshaid K.
Jamshaid K.

Reputation: 4547

So, You are saving the values in SelectedDepartment property and accessing the Departments list. Which is never initialized so it would obviously be null.

Modify your GetBudgetsActuals method like this:

public BudgetsActualsViewModel GetBudgetsActuals()  
{
    ...
    BudgetsActualsViewModel budgetsActuals = new BudgetsActualsViewModel(){ Departments = new List<SelectListItem>() };
    // Query returning correct data from DB here

    for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
    {
        budgetsActuals.Departments
                      .Add(new SelectListItem 
                          { 
                              Text = ds.Tables[0].Rows[i]["Department"].ToString(), 
                              Value = ds.Tables[0].Rows[i]["YourRowId"].ToString() 
                          });
    }
    return budgetsActuals;
}

And this is how your View should look like:

@model BudgetDemo.Models.BudgetsActualsViewModel
@Html.DropDownListFor(m => m.SelectedDepartment, Model.Departments))

Notice, we got rid of the foreach loop. We need DropDownListFor() method to be called only once.

UPDATE

public class BudgetsActualsViewModel
{
    [Display(Name = "Cost Center/Department")]
    [Required(ErrorMessage = "Cost Center/Department is required.")]
    [StringLength(62)]
    public string SelectedDepartment { get; set; }
    public List<SelectListItem> Departments { get; set; } // Modify it to list instead IEnumerable.
}

Upvotes: 1

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