C#•11mo ago

Is there any way to conditionally set a property with EF `.ExecuteUpdateAsync()`?

Right now, I'm doing

var thing = await _ctx.Things.FirstOrDefaultAsync(t => t.Id == req.Id);
if (thing.Name != req.Name) thing.Name = req.Name;
if (thing.Count != req.Count) thing.Count = req.Count;
await _ctx.SaveChangesAsync();

var thing = await _ctx.Things.FirstOrDefaultAsync(t => t.Id == req.Id);
if (thing.Name != req.Name) thing.Name = req.Name;
if (thing.Count != req.Count) thing.Count = req.Count;
await _ctx.SaveChangesAsync();

but I'm not sure how would I do something similar, as in, something that avoids setting x.Name = x.Name, with the Execute method. Something like

var rows = await _ctx.Things.Where(t => t.Id == req.Id)
    .ExecuteUpdateAsync(props => props
        .SetPropertyIf(t => t.Name != req.Name, t => t.Name, req.Name)
        .SetPropertyIf(t => t.Count != req.Count, t => t.Count, req.Count))

var rows = await _ctx.Things.Where(t => t.Id == req.Id)
    .ExecuteUpdateAsync(props => props
        .SetPropertyIf(t => t.Name != req.Name, t => t.Name, req.Name)
        .SetPropertyIf(t => t.Count != req.Count, t => t.Count, req.Count))

but no such thing seems to exist.

11 Replies

Bailey•11mo ago

I do not know what you exactly need. However the object is tracked. so if you set the value and it is the same. EF will notice that. Save wont do anything. Before you save you can use the property in the _ctx to check if there are any changes var thing = await _ctx.Things.FirstOrDefaultAsync(t => t.Id == req.Id); thing.Name = req.Name; thing.Count = req.Count; await _ctx.SaveChangesAsync(); // only saves if there are any changes. You //can also check for changes using: if (_ctx.ChangeTracker.HasChanges()) await _ctx.SaveChangesAsync();

AngiusOP•11mo ago

Yes, which is why I'm doing it this way But I'd like to start using the .Execute method here to save on a database call

Bailey•11mo ago

the code below essantial does the same. The object is taken. The values are updated and no if functions required var thing = await _ctx.Things.FirstOrDefaultAsync(t => t.Id == req.Id); thing.Name = req.Name; thing.Count = req.Count; if (_ctx.ChangeTracker.HasChanges()) await _ctx.SaveChangesAsync(); you can also use sql commands with EF. but its build for not using sql _ctx.ExecuteSql

Omnissiah•11mo ago

what sql would this translate to, an inline if? i don't think i have ever seen that but i could be wrong

AngiusOP•11mo ago

It would just not add a set clause to the resulting SQL

Omnissiah•11mo ago

have you tried if ?: is translated?

AngiusOP•11mo ago

Though... I guess it wouldn't know without executing some other query Just a simple bool would also work, I guess

var rows = await _ctx.Things.Where(t => t.Id == req.Id)
    .ExecuteUpdateAsync(props => props
        .SetPropertyIf(req.Name is not null, t => t.Name, req.Name)
        .SetPropertyIf(req.Count is not null, t => t.Count, req.Count))

var rows = await _ctx.Things.Where(t => t.Id == req.Id)
    .ExecuteUpdateAsync(props => props
        .SetPropertyIf(req.Name is not null, t => t.Name, req.Name)
        .SetPropertyIf(req.Count is not null, t => t.Count, req.Count))

Omnissiah•11mo ago

with just a null condition (on external value) you could make an extension (to add the expression)

AngiusOP•11mo ago

In case req.Name is null it would generate

UPDATE things t
WHERE t.Id = @id
SET  t.Count = @count

UPDATE things t
WHERE t.Id = @id
SET  t.Count = @count

If neither is null,

UPDATE things t
WHERE t.Id = @id
SET  t.Count = @count, t.Name = @name

UPDATE things t
WHERE t.Id = @id
SET  t.Count = @count, t.Name = @name

Huh, an extension method on the expression, maybe?

Omnissiah•11mo ago

that's what i said

AngiusOP•11mo ago

Yeah That could work

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Is there any way to *conditionally* set a property with EF `.ExecuteUpdateAsync()`?

Is there any way to conditionally set a property with EF `.ExecuteUpdateAsync()`?