Aspnetcore: Selectable dropdown list binding issue

[Gyciauskas]

Hey,

Last several days i'm totally struggling with selectable list or it call maybe drop-down list (I'm back-end developer). Anyway, can't make it working with drop-down list if drop-down list items is dynamic get data from server.

This is enum drop-down list working great:

        <div class="form-group">
                <select class="form-control" @bind(_user.UserType)>
                    @foreach (var userType in Enum.GetValues(typeof(UserType)))
                    {
                        <option>@userType</option>
                    }
                </select>
        </div>

This one is not building:

        <div class="form-group">
                <select class="form-control" @bind(_user.CompanyName)> // CompanyName - string
                    @foreach (var company in _companies) // _companies is List<Company> Company object contain Id and name
                    {
                        <option [email protected]>@company.name</option>
                    }
                </select>
            </div>
        </div>

Also possible that i'm just doing it wrong (I guess it 90% possibility). Can anyone tell what i'm doing wrong?

[rstropek]

I tried your code and it works fine for me. Here is my complete sample:

@page "/counter"

 <div class="form-group">
    <select class="form-control" bind="@_user.CompanyName"> // CompanyName - string
        @foreach (var company in _companies) // _companies is List<Company> Company object contain Id and name
        {
            <option [email protected]>@company.name</option>
        }
    </select>
     <button @onclick(Print)>Print</button>
</div>

@functions {
    public class Company
    {
        public string name { get; set; }

    }

    public class User
    {
        public string CompanyName { get; set; }
    }

    public User _user { get; set; } = new User { CompanyName = "" };

    public List<Company> _companies { get; set; } = new List<Company>
    {
        new Company { name = "Demo" },
        new Company { name = "Demo2" }
    };

    public void Print()
    {
        Console.WriteLine(_user.CompanyName);

    }
}

Does my sample code work for you? Did it help to find the root cause of your problem?

[Gyciauskas]

I pasted your code to new blazer project. Very strange, but Console output line where should be company name is empty..

[rstropek]

Do you use 0.1.0? I use the new binding syntax -> latest build/NuGet packages. If you use 0.1.0, you have to switch to old @bind. Does that help?

[Gyciauskas]

Yes, I have used 0.1.0 version. After switched to old one, yea it now working. So that great, thanks!

[kieronlanning]

I'm getting an odd issue when trying to bind nullable ints. Is this related to the new syntax?

[Gyciauskas]

Binding nullable int to input causes null reference exception aspnet/Blazor#466 Look at this ticket

[conficient]

@kieronlanning try binding to a string property instead as a converter e.g.

public int? Value {get;set;}
public string ValueConverter {
get
  { 
    return Value?.value.ToString();
  }
set
  {
    Value = string.IsNullOrWhitespace(value) ? null : Int32.Parse(value);
  }
}

[kieronlanning]

@conficient Thanks, what I've ended up doing is something like this (dependent on the property type):

bind=@(object.Property ?? 0)

[conficient]

@kieronlanning that's okay if you only wanted a one-way binding. My converter was intended to work for two-way bindings. Hopefully 0.2.0 will add support for different types.

[kieronlanning]

@conficient Ahhh, I didn't realise.

Thanks!

[SteveSandersonMS]

Closing as the original issue was confirmed as resolved.