Within a project I have a database table with the following columns
I would like to be able to delete from this table all rows which have a matching SharingAgencyId and ReceivingAgencyId values that I can pass in.
What I have tried so far:
public static ICollection<SecurityDataShare> UpdateSharedEntites(long conAgency, long recAgency)
{
ICollection<SecurityDataShare> agShares = null;
try
{
using (var context = new ProjSecurityEntities(string.Empty))
{
agShares = (from a in context.SecurityDataShares
.Where(c => c.ReceivingAgencyId == recAgency && c.SharingAgencyId == conAgency)
select a);
}
}
catch (Exception ex)
{
//ToDo
throw;
}
}
My thought process was to retrieve the records where the id's matched the parameters passed in and then using a foreach loop iterate through (agShare) and remove each row followed by saving my changes. With the current implementation I don't seem to have access to any of the Delete methods.
Looking to the example above I'd appreciate any suggestions on how to remove the rows within the table that contained a value of 43 and 39 using dbContext.
Cheers
If I understand right, your DbContext's properties, like SecurityDataShares should be typed as IDbSet<SecurityDataShare>. If that's correct, you should be able to use this Remove method.
foreach(var agShare in agShares) {
context.SecurityDataShares.Remove(agShare);
}
context.SaveChanges();
Be aware that this creates a separate SQL statement for deleting these objects. If you expect the number of objects to be rather large, you may want to use a stored procedure instead.
Entity Framework doesn't make it easy to run a single command to delete multiple rows (that I know of). My preference is to run a SQL statement directly for multi-entity updates/deletes using native sql with the dbcontext of sorts.
you can also pass datatable to the stored procedure with database contain dynamic type table of your type and
use that table into stored procedure for deleting matching rows from Database table.
Related
I am using Mirth Connect 3.5.0.8232. I have created a persisted connection to an Oracle database and using it throughout my source and destination connectors. One of the methods Mirth provides for talking with the database is executeUpdateAndGetGeneratedKeys. It would be quite useful for insert statements that would return the primary keys for the inserted rows.
My question is - how do you specify WHICH columns to return? Running the provided function works, but returns ROWID in the CachedRowSet, which is not what I want.
As far as I understood, which columns to return depends on the type of the database, and every database behaves differently. I am interested in Oracle specifically.
Thank you.
The executeUpdateAndGetGeneratedKeys method uses the Statement.RETURN_GENERATED_KEYS flag to signal to the driver that auto-generated keys should be returned. However, from the Oracle docs:
If key columns are not explicitly indicated, then Oracle JDBC drivers cannot identify which columns need to be retrieved. When a column name or column index array is used, Oracle JDBC drivers can identify which columns contain auto-generated keys that you want to retrieve. However, when the Statement.RETURN_GENERATED_KEYS integer flag is used, Oracle JDBC drivers cannot identify these columns. When the integer flag is used to indicate that auto-generated keys are to be returned, the ROWID pseudo column is returned as key. The ROWID can be then fetched from the ResultSet object and can be used to retrieved other columns.
So instead, try using their suggestion of passing in a column name array to prepareStatement:
var dbConn;
try {
dbConn = DatabaseConnectionFactory.createDatabaseConnection('oracle.jdbc.driver.OracleDriver','jdbc:oracle:thin:#localhost:1521:DBNAME','user','pass');
// Create a Java String array directly
var keyColumns = java.lang.reflect.Array.newInstance(java.lang.String, 1);
keyColumns[0] = 'id';
var ps = dbConn.getConnection().prepareStatement('INSERT INTO tablename (columnname) VALUES (?)', keyColumns);
try {
// Set variables here
ps.setObject(1, 'test');
ps.executeUpdate();
var result = ps.getGeneratedKeys();
result.next();
var generatedKey = result.getObject(1);
logger.info(generatedKey);
} finally {
ps.close();
}
} finally {
if (dbConn) {
dbConn.close();
}
}
db.AdDetails.Where( u => u.OwnerGUID == CurrentUserProviderKey)
I have an adDetails table that has an OwnerGUID field.
I want to pull out only ad details that belong to the currenly logged in user.
My query does not show any where clauses in the SQL when I look at it in the debugger.
Can someone help me figure out what is wrong with my statement and if all rows in the table will be brought back then all 10K records put though a where on the webserver?
I am really new to this.
Using the Where extension method will filter down the results.
Queries in Entity Framweork are not executed until you iterate over them. If you do:
var query = db.Where(u => u.OwnerGUID == key);
This does not execute the query. When you do the following:
var list = list.ToList();
OR
foreach( var item in query) { ... }
That is when the query will be executed in SQL. The results should be filtered with your WHERE clause at this point.
I have created a linq query that returns my required data, I now have a new requirement and need to add an extra field into the returned results. My entity contains an ID field that I am trying to map against another table without to much luck.
This is what I have so far.
Dictionary<int, string> itemDescriptions = new Dictionary<int, string>();
foreach (var item in ItemDetails)
{
itemDescriptions.Add(item.ItemID, item.ItemDescription);
}
DB.TestDatabase db = new DB.TestDatabase(Common.GetOSConnectionString());
List<Transaction> transactionDetails = (from t db.Transactions
where t.CardID == CardID.ToString()
select new Transaction
{
ItemTypeID= t.ItemTypeID,
TransactionAmount = t.TransactionAmount,
ItemDescription = itemDescriptions.Select(r=>r.Key==itemTypeID).ToString()
}).ToList();
What I am trying to do is key the value from the dictonary where the key = itemTypeID
I am getting this error.
Local sequence cannot be used in LINQ to SQL implementations of query operators except the Contains operator.
What do I need to modify?
This is a duplicate of this question. The problem you're having is because you're trying to match an in-memory collection (itemDescriptions) with a DB table. Because of the way LINQ2SQL works it's trying to do this in the DB which is not possible.
There are essentially three options (unless I'm missing something)
1) refactor your query so you pass a simple primitive object to the query that can be passed accross to the DB (only good if itemDescriptions is a small set)
2) In your query use:
from t db.Transactions.ToList()
...
3) Get back the objects you need as you're doing, then populate ItemDescription in a second step.
Bear in mind that the second option will force LINQ to evaluate the query and return all transactions to your code that will then be operated on in memory. If the transaction table is large this will not be quick!
I am trying to figure out how to dynamically specify the properties for my select clause in a linq query.
Lets say I have a collection of employee objects. At run time, the end user will be specifying which properties they would like to see for those employees, so I need to be able to dynamically construct my Linq select clause.
I have used the dynamic Linq library, but I prefer not to use that, because it requires me to build a string to pass to the select method. I'd like to understand how to do this via Expressions.
This looks like something that fits more with your requirements of not using dynamic linq.
Use Reflection to get the dynamic Column Values
//columns variable has column name as comma separated String which you
can save in DB //example string columns ="Name,Id,Age";
var strColumns =columns.split(,);
foreach(var myObject in MyObjectcollection)
{
for(int index =0;index<strColumns.count();index++)
{
//Create a collection of objects
mycollection.add(myObject.GetType().GetProperty(strColumns[index]).GetValue(myObject, null));
}
}
I have recently developed a C# application using Linq.
I am getting from an external database a list of profiles I need to process, some are new and some are already in the database, and need to be updated.
What I do today is go over the profile list and check each profile if such exists I update otherwise I insert - this solution is working fine.
I am sure there is a way to use bulk insert/update something like UPDATE ON DUPLICATE, this way I can save time since the files I get are huge and bulk insert/update is known to have better performance. I would like to avoid the iteration I am now using.
insertall doesn't work for already stored rows, I need the combination of both update and insert
Here is my code, Your help is highly appreciated.
foreach (Profile tmpProfile in profiles)
{
try
{
var matchedProfile = (from c in db.ProfileEntities
where c.ProfileId == tmpProfile.Id
select c).SingleOrDefault();
if (matchedProfile == null)
{
//Insert
db.ProfileEntities.InsertOnSubmit(EntityMapper.ToEntity(tmpProfile));
}
else
{
//Update
EntityMapper.ToEntity(ref matchedProfile, tmpProfile);
}
}
catch (System.Data.SqlServerCe.SqlCeException sqlExec)
{
}
catch (Exception e)
{
}
}
db.SubmitChanges();
One possible optimisation would be to create a list of all the items that you have from the external application, and then read all items from the database that match at once, instead of doing multiple round trips.
You can then update all of those, insert all of the ones that are left and call SubmitChanges at the end - you will then have 2 round trips to the database instead of one per profile retreived externally.
I don't know of any bulk update or insert features in Linq to SQL