I posted this question yesterday evening, which has led me to discover a huge problem!
I have a decimal column in my database called Units, anytime I set the value of the column to a NON ZERO, and SubmitChanges the column updates with the new value. If I try to set the value of the column to ZERO, the SubmitChanges does not update the column.
data.Units = this.ReadProperty<decimal>(UnitsProperty);
data.UnitPrice = this.ReadProperty<decimal>(UnitPriceProperty);
data.Price = this.ReadProperty<decimal>(PriceProperty);
I've taken a look at the DataContext log and I can see that the field with the ZERO value is not included in the query. Even if I try to hard code the change Linq ignores it.
data.Units = 0;
data.UnitPrice = 0;
data.Price = 0;
Needless to say this is killing me! Any ideas why this happening?
Solution
I figured out my problem with the help of the SO community. My problem was being caused by the fact when I created my entity to attach, the default value of the column was set to zero, so when it tried to assign the value to zero ... LinqToSql says hey ... nothing changed, so I am not updating the value.
What I am doing now ... just to make it work is the following:
ctx.DataContext.InvoiceItems.Attach(data, true);
That seems to force all the values to write themselves to the database. This works for now.
I have tried to reproduce this with a the following code, but for me it works.
using (DataClasses1DataContext ctx = new DataClasses1DataContext())
{
var obj = ctx.DecimalColumnTables.First();
Debug.Assert(obj.B != 0);
obj.B = 0;
ctx.SubmitChanges();
}
So I think there must be something special in your domain that causes this. I suggest you to create a such simple repro with your domain model and see what happens.
LINQ to SQL ignores updates to the current value, so if the field was already zero, you may not see any updates.
Off: The OR/M you use is LINQ to SQL. LINQ is the name of the querying capability in .NET, but LINQ does not define nor implement any update logic. So the issue relates to LINQ to SQL, not LINQ.
Obvious question, but are you sure the column is mapped in the dbml / mapping file?
Also - is it a calculated column? (i.e. price => units * unitprice)
I figured out my problem with the help of the SO community. My problem was being caused by the fact when I created my entity to attach, the default value of the column was set to zero, so when it tried to assign the value to zero ... LinqToSql says hey ... nothing changed, so I am not updating the value.
What I am doing now ... just to make it work is the following:
ctx.DataContext.InvoiceItems.Attach(data, true);
That seems to force all the values to write themselves to the database. This works for now.
Some more information ... I figured out my problem ... it's more of a lack of understanding about LinqToSql ... where I am doing:
private void Child_Update(Invoice parent)
{
using (var ctx = Csla.Data.ContextManager
.GetManager(Database.ApplicationConnection, false))
{
var data = new Gimli.Data.InvoiceItem()
{
InvoiceItemId = ReadProperty(InvoiceItemIdProperty)
};
ctx.DataContext.InvoiceItems.Attach(data);
if (this.IsSelfDirty)
{
// Update properties
}
}
}
I thought this would load the original values ... what happens is that it creates a new object with default values ... empty values, like 0 for decimals, Guid.Empty for uniqueidentifiers and so on.
So when it updates the properties it sees the Units already as 0 and it sets it to zero. Well LinqToSql doesn't recognize this as a change so it doesn't up date the field. So what I have had to do is the following:
ctx.DataContext.InvoiceItems.Attach(data, true);
Now all the modifications are generated in the update statement whether there is really a change or not. This works ... seems a bit hackish!
The correct answer is as many pointed out to use the special overload of Attach which accepts a boolean parameter to consider it as modified, (make the mistake of using another overload and it simply won't work):
ctx.DataContext.InvoiceItems.Attach(data, true);
Note however that you still might need to have a "Version" column in the table of type "timestamp".
I had this problem and all the suggestions I'd seen didn't apply or work.
But I found I had made a very simple mistake!
When updating the property I was actually calling a custom Set method (because there were other things that needed to be changed in response to the main property in question).
After hours of head scratching I noticed that my Set method was updating the private member not the public property, i.e. this._Walking = value;
All I had to do was change this to this.Walking = value; and it all started to work!
Related
I'm experimenting with C#/.net/WPF all for the first time. I've created a project and set up a datasource (just a table with some sample data) and created two tableadapters named Prods and Prods1 - the latter has a filter applied in the query to return slightly different results. I've dropped both tables on my form and both dutifully display their respective data.
I thought I would then swap the data source for each. So the default generated Window_Loaded:
MSDSTest.prodtestDataSet prodtestDataSet = ((MSDSTest.prodtestDataSet)(this.FindResource("prodtestDataSet")));
// Load data into the table Prods. You can modify this code as needed.
MSDSTest.prodtestDataSetTableAdapters.ProdsTableAdapter prodtestDataSetProdsTableAdapter = new MSDSTest.prodtestDataSetTableAdapters.ProdsTableAdapter();
prodtestDataSetProdsTableAdapter.Fill(prodtestDataSet.Prods);
System.Windows.Data.CollectionViewSource prodsViewSource = ((System.Windows.Data.CollectionViewSource)(this.FindResource("prodsViewSource")));
prodsViewSource.View.MoveCurrentToFirst();
// Load data into the table Prods1. You can modify this code as needed.
MSDSTest.prodtestDataSetTableAdapters.Prods1TableAdapter prodtestDataSetProds1TableAdapter = new MSDSTest.prodtestDataSetTableAdapters.Prods1TableAdapter();
prodtestDataSetProds1TableAdapter.Fill(prodtestDataSet.Prods1);
System.Windows.Data.CollectionViewSource prods1ViewSource = ((System.Windows.Data.CollectionViewSource)(this.FindResource("prods1ViewSource")));
prods1ViewSource.View.MoveCurrentToFirst();
I now want to make the first data grid (prodsViewSource) instead display the data for the second table, and ignore the second table entirely. So, I changed that as follows:
MSDSTest.prodtestDataSet prodtestDataSet = ((MSDSTest.prodtestDataSet)(this.FindResource("prodtestDataSet")));
// Load data into the table Prods. You can modify this code as needed.
MSDSTest.prodtestDataSetTableAdapters.Prods1TableAdapter prodtestDataSetProdsTableAdapter = new MSDSTest.prodtestDataSetTableAdapters.Prods1TableAdapter();
prodtestDataSetProdsTableAdapter.Fill(prodtestDataSet.Prods1);
System.Windows.Data.CollectionViewSource prodsViewSource = ((System.Windows.Data.CollectionViewSource)(this.FindResource("prodsViewSource")));
prodsViewSource.View.MoveCurrentToFirst();
With the second block having been commented out.
I must be missing something fundamental - what I think I'm doing is redefining the prodtestDataSetProdsTableAddapter variable to use an instance of the prods1 table adapter, and then using that to populate the prodsViewSource grid on the form, but I end up with a blank. Where's my error?
...
Well, I posted this after beating my head against it for an hour and, minutes later, realized the FAR easier thing to do is to just change the datacontext property of the grid in question.
I would still like to understand why doing it the vastly more complicated-bordering-on-Rube-Goldbergian way didn't work, though, so if anyone can explain that, it would still be welcome.
I'm looking at updating stored values in a RethinkDB using the C# RethinkDB.Driver library and I'm just not getting it right.
I can achieve an update by getting the result, altering that object then making a separate call to update with that object. When there are many calls to a record to update like this, the value being updated elsewhere whilst the application is working with the record.
TestingObject record = r.Db("test").Table("learning").Get("c8c54346-e35f-4025-8641-7117f12ebc5b").Run(_conn);
record.fieldNameIntValue = record.fieldNameIntValue + 1;
var result = r.Db("test").Table("learning").Get("c8c54346-e35f-4025-8641-7117f12ebc5b").Update(record).Run(_conn);
I've been trying something along these lines :
var result = r.Db("test").Table("learning").Get("c8c54346-e35f-4025-8641-7117f12ebc5b").Update(row => row["fieldNameIntValue"].Add(1)).Run(_conn);
but the result errors with Inserted value must be an OBJECT (got NUMBER):101 which suggests this is only passing the field value back instead of updating the object.
Ideally I'd like to update multiple columns at once, any advice is appreciated :)
This is an example that works in the ReQL data explorer. You can chain as may filters before the update as you want. I assume this will translate to the C# Driver, but I dont have any experience with that.
r.db('database').table('tablename').update({clicks: r.row("clicks").add(1)}).run().then(function(result){ ...
Thanks T Resudek your answer and a clearer head helped emphasised the need to map the calculation to the property.
Looking at the javadocs for update it has HashMap method which I followed with the c# library and it works.
var result = r.Db("test").Table("learning").Get("c8c54346-e35f-4025-8641-7117f12ebc5b").Update(row => r.HashMap("fieldNameIntValue",row["fieldNameIntValue"].Add(1))).Run(_conn);
I'd be interested to know if this is the right way or was a better way.
My program is writing records to a db table. So far, it has written about 58 new records to this table. All of a sudden, I get an error message saying "Row not found or changed." Which is odd, because I'm inserting a new record, not trying to find one or update an existing one. Here's the small bit of code that I'm using to create an object and then insert to the table:
// create new comment object
var comment = new Comment
{
TableName = "Circuit",
TableKey = circuitId,
Text = remarks,
CreatedOn = DateTime.Now,
CreatedByName = "loadCC03Circuits",
CreatedByUupic = "000000000"
};
cimsContext.Comments.InsertOnSubmit(comment);
cimsContext.SubmitChanges();
I'm not quite sure what to do, at this point. Each field has a value, there are no nulls. And, as I said, 58 records have already been written out by this very same bit of code before this happens so, other than the data being off (which, according to the field values in my debugger session, are not) I'm not quite sure what else to check. Any advice?
EDIT: I added an answer below that made this problem go away. But, I'm not sure why this solution worked.
I found a solution, but not the "answer". The solution, in this case, was to make a variable that contained the DateTime.Now value:
var dateNow = DateTime.Now;
And I changed the affected line of code to look like this:
CreatedOn = dateNow,
Wonders of wonders, I no longer received the error. I'm not sure why this fixed the problem, I only tried this on a suggestion from a co-worker. He theorizes that the sandbox database that I'm working is sluggish and could be affecting the DateTime.Now function. Regardless, this made that issue go away. I wish I had a definitive answer, though. I hate making a problem go away when I don't understand why the solution worked.
Given the following code (which is mostly irrelevant except for the last two lines), what would your method be to get the value of the identity field for the new record that was just created? Would you make a second call to the database to retrieve it based on the primary key of the object (which could be problematic if there's not one), or based on the last inserted record (which could be problematic with multithreaded apps) or is there maybe a more clever way to get the new value back at the same time you are making the insert?
Seems like there should be a way to get an Identity back based on the insert operation that was just made rather than having to query for it based on other means.
public void Insert(O obj)
{
var sqlCmd = new SqlCommand() { Connection = con.Conn };
var sqlParams = new SqlParameters(sqlCmd.Parameters, obj);
var props = obj.Properties.Where(o => !o.IsIdentity);
InsertQuery qry = new InsertQuery(this.TableAlias);
qry.FieldValuePairs = props.Select(o => new SqlValuePair(o.Alias, sqlParams.Add(o))).ToList();
sqlCmd.CommandText = qry.ToString();
sqlCmd.ExecuteNonQuery();
}
EDIT: While this question isn't a duplicate in the strictest manner, it's almost identical to this one which has some really good answers: Best way to get identity of inserted row?
It strongly depends on your database server. For example for Microsoft SQL Server you can get the value of the ##IDENTITY variable, that contains the last identity value assigned.
To prevent race conditions you must keep the insert query and the variable read inside a transaction.
Another solution could be to create a stored procedure for every type of insert you have to do and make it return the identity value and accept the insert arguments.
Otherwise, inside a transaction you can implement whatever ID assignment logic you want and be preserved from concurrency problems.
Afaik there is not finished way.
I solved by using client generated ids (guid) so that my method generated the id and returns it to the caller.
Perhaps you can analyse some SqlServer systables in order to see what has last changed. But you would get concurrency issues (What if someone else inserts a very similar record).
So I would recommend a strategy change and generate the id's on the clients
You can take a look at : this link.
I may add that to avoid the fact that multiple rows can exist, you can use "Transactions", make the Insert and the select methods in the same transaction.
Good luck.
The proper approach is to learn sql.
You can do a SQL command followed by a SELECT in one run, so you can go in and return the assigned identity.
See
Hey guys, I'm having a weird time with Linq-To-SQL
I'm building a postit system that allows people to make postits and attach them to multiple objects. The database for this is a table that has the postits themselves (id, message, etc) and a linkstable which holds the records to which a postit is attached.
the weird thing I'm experiancing is the following.
When I retrieve an object from the database (using Linq-To-SQL), do some data changing and submit it again, I experience no trouble whatsoever.
Yet, when I try to make a new one I get an exception in the Submitchanges method in the datacontext: Specified Cast is not valid.
I've been looking on the web and mostly it involves some change in the mapping, but this shouldn't be the case as I can update without any problems.
T_PostIt np = new T_PostIt();
np.CreatedOn = DateTime.Now;
np.CreatedBy = Request.ServerVariables["REMOTE_USER"].ToString();
np.MarkedForDeletion = false;
np.Message = txtNewPostitMessage.Text;
np.ModifiedBy = Request.ServerVariables["REMOTE_USER"].ToString();
foreach (int i in ServerIds)
{
T_PostIt_Link pil = new T_PostIt_Link();
pil.LinkType = 'S';
pil.LinkID = i;
pil.MarkedForDeletion = false;
np.T_PostIt_Links.Add(pil);
}
dc.T_PostIts.InsertOnSubmit(np);
dc.SubmitChanges();
I use the above code and can't seem to get what I'm doing wrong.
help anyone?
Have you tried updating the properties one by one, and then save the changes back to the database? It could be that updating the entity only fails when one specific value has changed. If I may guess, it could be that the value of CreatedOn cannot be cast to a valid DateTime in the database (due to culture settings). That would explain why updating goes OK - you're not changing the value of CreatedOn here. You do, however, when inserting a new entity.
Edit: maybe this is the problem you're facing. Also, be sure to read this thread, where the topic starter eventually points to the first thread mentioning that it is an apparant bug in Linq2Sql.