populate the textbox from the value stored in the database table

sblb 1,166

Hi,
I've a class model as below

public partial class Developer  
  
    {  
        public int Id { get; set; }     
        public int _currentYear = DateTime.Today.Year;       
        public string EnvT { get { return _currentYear.ToString(); } }    
}

I want to retrieve EnvT in TextBox as below

<EditForm Model="@dev" OnValidSubmit="@OnValidSubmit">  
    <DataAnnotationsValidator />  
 <RadzenTextBox style="width: 100%;" Name="Numéro EnvT" @bind-Value=@dev.EnvT Disabled=true/>  
                        <ValidationMessage For="@(() => dev.EnvT)" />  
</EditForm>

Edit razor page is

<FormEdit ButtonText="Update" dev="dev"  
      OnValidSubmit="@EditDeveloper" />  
  
@code {  
  
    [Parameter] public int developerId { get; set; }  
    Developer dev = new Developer();  
  
    protected async override Task OnParametersSetAsync()  
    {  
        dev = await http.GetFromJsonAsync<Developer>($"api/developer/{developerId}");  
  
    }  
  
    async Task EditDeveloper()  
    {  
        await http.PutAsJsonAsync("api/developer", dev);  
        await js.InvokeVoidAsync("alert", $"Updated Successfully!");  
        uriHelper.NavigateTo("developer");  
    }

I've a message error : Property or indexer 'property' cannot be assigned to -- it is read only

I don't how why I've this error.
Do I have to do this to find the EnvT value in the database table?

Thanks in advance!

AgaveJoe 26,181 Reputation points

2022-08-25T13:21:10.987+00:00

You specifically set the EnvT property to readonly that always returns DateTime.Today.Year.

Do I have to do this to find the EnvT value in the database table?

I'm not sure. If EnvT is a field in the database then your design makes little sense. Perhaps the intention is to create a default value during an insert when EnvT is empty?

Is there anyway you can explain how the code is intended to function?
Viorel 111.8K Reputation points

2022-08-25T13:50:56.787+00:00

Does it work if you change the definition to public string EnvT { get { return _currentYear.ToString(); } set { } } for researching purposes?
sblb 1,166 Reputation points

2022-08-25T14:33:41.797+00:00

If I change model class as public string EnvT { get { return _currentYear.ToString(); } set { } } it's ok! That's return the value EnvT
thanks!

I tried private set{} and it didn't work. Do you know why?
AgaveJoe 26,181 Reputation points

2022-08-25T15:05:54.66+00:00

I tried private set{} and it didn't work. Do you know why?

The Private access modifier only allows methods within the class to modify the property.

Property Access control

Access modifiers are a fundamental C# feature.

Access Modifiers (C# Programming Guide)

This update can not be the actual fix since the get always returns DateTime.Today.Year.ToString(). The set logic uses an empty set while the property has a defined field. In other words, your design makes no logical sense. It might seem to work today but next year EnvT will return 2023 while the table could contain 2022.

2 answers

sblb 1,166 Reputation points

2022-08-25T15:26:00.833+00:00

If EnvT is a field in the database then your design makes little sense.

Why?

I want to fill EnvT, which is defined in database, when I create and edit the line from DataGrid (CRUD).
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sblb 1,166 Reputation points

2022-08-25T15:44:25.407+00:00

It might seem to work today but next year EnvT will return 2023 while the table could contain 2022.

It's exactly what I want; each line of my table will have 2022 for EnvT and when the Year Change the new line of the table will take 2023.
Is there a problem with doing this?
Do you have a counter example?
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AgaveJoe 26,181 Reputation points

2022-08-25T17:37:32.413+00:00

Is there a problem with doing this?

The problem, like your other threads, is you are coping and pasting code but have no idea what the code does. Spend a few minutes testing the code to make sure the logic functions as you expect.

static async Task Main(string[] args) { Developer d = new Developer() { Id = 1, EnvT = "2021" }; Console.WriteLine($"{d.Id}\t{d.EnvT}"); d.EnvT = "2023"; Console.WriteLine($"{d.Id}\t{d.EnvT}"); } } public partial class Developer { public int Id { get; set; } public int _currentYear = DateTime.Today.Year; public string EnvT { get { return _currentYear.ToString(); } set { } } }

Results

1 2022 1 2022

Do you have a counter example?

So other forum member understand what counter means in your application... The Id start at 1 each time a new year begins. There is no way anyone would understand this by reading your code.

To answer your question, the community provided two working examples in previous threads. Are you asking for yet another example? If so, what is wrong with the examples already provided?
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