How to do Edit action with view model?

Question

I’m trying to do in my project the editing part of the data that was registered. Well, the data log part is working fine, but now I need to edit this data. Before, I looked around the web to see what I could find about it. I found link no Sous. Only I didn’t understand the code right...

Could someone help me?

Answer 1

Basically it is the same principle of creation, but some more details need to be observed:

• The identifier of the Model original needs to exist somehow;
• You will need to bring from the bank the Model twice: once to fill the Viewmodel and another to update it.

An editing cliché of a Model Produto two-property, Id and Nome, would be something like:

public async Task<ActionResult> Editar(int? id)
{
    if (id == null)
    {
        return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
    }
    Produto produto = await db.Produtos.FindAsync(id);
    if (produto == null)
    {
        return HttpNotFound();
    }

    var produtoViewModel = new ProdutoViewModel 
    {
        ProdutoId = produto.ProdutoId,
        Nome = produto.Nome
    };

    return View(produtoViewModel);
}

The construction of its View will be exactly the same as the construction using a Model. What changes is only the note @model:

@model MeuProjeto.ViewModels.ProdutoViewModel

In the POST:

[HttpPost]
public async Task<ActionResult> Editar(ProdutoViewModel viewModel)
{
    if (ModelState.IsValid)
    {
        var produto = db.Produtos.FirstOrDefault(p => p.ProdutoId == viewModel.ProdutoId);

        if (produto == null)
        {
            return HttpNotFound();
        }

        produto.Nome = viewModel.Nome;

        db.Entry(produto).State = EntityState.Modified;
        await db.SaveChangesAsync();
        return RedirectToAction("Index");
    }

    return View(viewModel);
}

Advantages of the approach:

• Security: You do not directly expose your Models on forms;
• Flexibility: more specific validation rules without necessarily impacting the Model.

Disadvantages of the approach:

• Complexity: your system will inevitably get bigger and more complex, and maintenance will be more difficult;
• Rework: extend a Model will mean extending all the Viewmodels associated with Model.