Unable to catch DbUpdateConcurrencyException and throw UserFriendlyException

Question

I am using ASP.NET Boilerplate with Code-First Entity Framework and MVC 5. I want to handle concurrency. In the Update method, I put Timestamp data annotation for RowVersion field in my entity.

In the manager of my entity and in Update operation, I am trying to catch DbUpdateConcurrencyException exception and throw UserFriendlyException but because UpdateAsync is asynchronous, I don't know where to handle the exception.

Where should I handle this exception to be user-friendly and not to see Internal Server Error?

public abstract class BaseFullAuditedEntity : FullAuditedEntity<Guid>
{
    [Timestamp]
    public byte[] RowVersion { get; set; }
}

public class Branch : BaseFullAuditedEntity
{
    public string Name { get; set; }
}

Manager code:

public interface IBranchManager : IDomainService
{
    Task<Branch> Update(Branch branch, byte[] RowVersion);
}

public class BranchManager : DomainService, IBranchManager
{
    private IRepository<Branch, Guid> _branchRepository { get; }

    public async Task<Branch> Update(Branch branch, byte[] RowVersion)
    {
        try
        {
            return await _branchRepository.UpdateAsync(branch);
        }
        catch (DbUpdateConcurrencyException ex)
        {
            throw new UserFriendlyException("Update Concurrency Happened");
        }
    }
}

Answer 1

UpdateAsync(branch) only adds branch to the context.

Inject IUnitOfWorkManager and await SaveChangesAsync():

try
{
    await _branchRepository.UpdateAsync(branch);
    await _unitOfWorkManager.Current.SaveChangesAsync(); // Add this
    return branch;
}
catch (DbUpdateConcurrencyException ex)
{
    throw new UserFriendlyException("Update Concurrency Happened");
}

Alternatively, override SaveChanges and SaveChangesAsync in your DbContext to catch for all entities:

public override int SaveChanges()
{
    try
    {
        return base.SaveChanges();
    }
    catch (DbUpdateConcurrencyException ex)
    {
        throw new UserFriendlyException("Update Concurrency Happened");
    }
}

public override async Task<int> SaveChangesAsync()
{
    try
    {
        return await base.SaveChangesAsync();
    }
    catch (DbUpdateConcurrencyException ex)
    {
        throw new UserFriendlyException("Update Concurrency Happened");
    }
}