Asp.Net Web V4 -并发检查

Question

下面的代码是从Wep v4脚手架工具生成的。

放置法

public IHttpActionResult Put([FromODataUri] string key, Delta<Product> patch)
{
    Validate(patch.GetEntity());

    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    Product product = db.Products.Find(key);
    if (product == null)
    {
        return NotFound();
    }

    patch.Put(product);

    try
    {
        db.SaveChanges();
    }
    catch (DbUpdateConcurrencyException)
    {
        if (!ProductExists(key))
        {
            return NotFound();
        }
        else
        {
            throw;
        }
    }

    return Updated(product);
}

贴片法：

[AcceptVerbs("PATCH", "MERGE")]
public IHttpActionResult Patch([FromODataUri] string key, Delta<Product> patch)
{
    Validate(patch.GetEntity());

    if (!ModelState.IsValid)
    {
        return BadRequest(ModelState);
    }

    Product product = db.Products.Find(key);
    if (product == null)
    {
        return NotFound();
    }

    patch.Patch(product);

    try
    {
        db.SaveChanges();
    }
    catch (DbUpdateConcurrencyException)
    {
        if (!ProductExists(key))
        {
            return NotFound();
        }
        else
        {
            throw;
        }
    }

    return Updated(product);
}

中的Rowversion字段

[Timestamp]
public byte[] RowVersion { get; set; }

问题：

1. 我需要实现并发性检查。如何以Odata方式(使用Etag)检查乐观并发性？
2. 在上面的代码中，DbUpdateConcurrencyException从未抛出。有什么原因吗？
3. 有一个名为[ConcurrencyCheck]的属性，它的用途是什么？我能用这个吗？

提供代码示例将是非常感谢的！

Answer 1

我解决了这个问题，检查我自己的并发字段，因为补丁或put做不到。这是我的代码，plato.TimeStamp是[Timestamp]属性。

   public async Task<IHttpActionResult> Put([FromODataUri] int key, Delta<Plato> patch)
    {
        Validate(patch.GetEntity());

        if (!ModelState.IsValid)
        {
            return BadRequest(ModelState);
        }

        Plato plato = await db.Platos.FindAsync(key);
        if (plato == null)
        {
            return NotFound();
        }
//Here save the current value in the DB
        string timeStamp = Convert.ToBase64String(plato.TimeStamp);
        patch.Put(plato);

        try
        {
//Here plato.TimeStamp is update from remote, must be equal to stored value
            if (timeStamp != Convert.ToBase64String(plato.TimeStamp))
            {
                throw new DbUpdateConcurrencyException();
            }
            await db.SaveChangesAsync();
        }
        catch (DbUpdateConcurrencyException)
        {
            if (!PlatoExists(key))
            {
                return NotFound();
            }
            else
            {
                throw;
            }
        }

        return Updated(plato);
    }