We Keep Coding

Deleting from tables

I have an old C# console application that I'm currently upgrading to use Entity Framework (latest version) code first.
I have 20+ tables that will be created in the database.
One of my methods is
static void DeleteModelInDb(Model pdModel, ExporterContext db) {
string[] tables = new string[] { "PD_COLUMN", "PD_COLUMN_EXTENDED", "PD_COLUMNRULE", "PD_COLUMNSOURCE", "PD_DB_PACKAGE", "PD_DB_PACKAGE_PROC_PARAMETER", "PD_DB_PACKAGE_PROCEDURE", "PD_DB_PACKAGE_TYPE", "PD_DB_PACKAGE_VARIABLE", "PD_DIAGRAM", "PD_DIAGRAM_TABLE", "PD_DOMAIN", "PD_DOMAIN_VALUES", "PD_INDEX", "PD_INDEX_COLUMN", "PD_JOIN", "PD_MODEL", "PD_MODEL_EXTENDED", "PD_MODEL_CHANGES", "PD_MODELSOURCE", "PD_PACKAGE", "PD_REFERENCE", "PD_RULE", "PD_TABLE", "PD_TABLE_EXTENDED", "PD_TABLE_CHANGES", "PD_TABLE_KEY", "PD_TABLE_KEY_COLUMN", "PD_TABLESOURCE", "PD_VIEW", "PD_VIEWCOLUMN", "PD_VIEWSOURCE" };
SqlConnection con = new SqlConnection("definition of con...");
con.Open();
SqlCommand com = con.CreateCommand();
foreach (string table in tables)
{
com.CommandText = "DELETE FROM " + table + " WHERE MODEL_CODE = '" + pdModel.Code + "'";
com.ExecuteNonQuery();
}
com.Dispose();
}
I would like to do something like this using Entity framework. But I don't want to write this delete code for every table.
var x = (from y in db.PdColumn
where y.ModelCode == pdModel.Code
select y).FirstOrDefault();
db.PdColumn.Remove(x);
db.SaveChanges();
Can someone help?

You should be able to abstract over the deletion code by having all the relevant entities implement an interface with the ModelCode property, then make a generic method for deleting (I am assuming that ModelCode is of type string below):
interface IEntityWithCode {
string ModelCode {get;}
}
void DeleteFromDbSet<T>(DBSet<T> dbset, string modelcode) where T: IEntityWithCode {
var x = (from y in dbset
where y.ModelCode == modelcode
select y).FirstOrDefault();
dbset.Remove(x);
}
Since C# does not support variance for classes, I don't think you can have a loop over a list of dbsets in your new DeleteModelInDb method without resorting to nasty reflection hacks, so it will have to look something like this
void DeleteModelInDb(YourDbContext context, string modelcode) {
DeleteFromDbSet(context.SomeTable, modelcode);
DeleteFromDbSet(context.SomeOtherTable, modelcode);
//and so on
}
(Disclaimer: The code is not tested as I don't have an EF core setup handy ATM)

Dapper parameters not working

I'm trying to use the Dapper orm with the following simple query:
var sqlString = new StringBuilder();
sqlString.Append("select a.acct AccountNumber,");
sqlString.Append(" b.first_name FirstName,");
sqlString.Append(" b.last_name LastName,");
sqlString.Append(" a.rr RrNumber,");
sqlString.Append(" c.addr1 AddressLine1,");
sqlString.Append(" c.addr2 AddressLine2,");
sqlString.Append(" c.addr3 AddressLine3,");
sqlString.Append(" c.addr4 AddressLine4,");
sqlString.Append(" c.addr5 AddressLine5,");
sqlString.Append(" c.addr6 AddressLine6,");
sqlString.Append(" c.addr7 AddressLine7,");
sqlString.Append(" c.addr8 AddressLine8 ");
sqlString.Append("from (pub.mfclac as a left join pub.mfcl as b on a.client=b.client) ");
sqlString.Append("left join pub.mfclad as c on a.client=c.client ");
sqlString.Append("where a.acct = '#ZYX'");
var connection = new OdbcConnection(_connectionString);
var result = connection.Query(sqlString.ToString(),
new
{
ZYX = accountNumber
});
However when I execute this with an accountNumber known to exist, dapper returns nothing. So I tried to remove the quotes to verify that the parameter is in fact being replaced with the account number, however the error being returned from the server indicates a syntax error around "#ZYX". Which means dapper is not replacing the parameter with it's given value. Any ideas why this is happening? From the limited documentation out there, this should 'just work'.
Edit1
Couldn't get this to work. Using string.format to insert the parameter as a work around.

There are two issues here; firstly (although you note this in your question) where a.acct = '#ZYX', under SQL rules, does not make use of any parameter - it looks to match the literal string that happens to include an # sign. For SQL-Server (see note below), the correct usage would be where a.acct = #ZYX.
However! Since you are use OdbcConnection, named parameters do not apply. If you are actually connecting to something like SQL-Server, I would strongly recommend using the pure ADO.NET clients, which have better features and performance than ODBC. However, if ODBC is your only option: it does not use named parameters. Until a few days ago, this would have represented a major problem, but as per Passing query parameters in Dapper using OleDb, the code (but not yet the NuGet package) now supports ODBC. If you build from source (or wait for the next release), you should be able to use:
...
where a.acct = ?
in your command, and:
var result = connection.Query(sqlString.ToString(),
new {
anythingYouLike = accountNumber
});
Note that the name (anythingYouLike) is not used by ODBC, so can be... anything you like. In a more complex scenario, for example:
.Execute(sql, new { id = 123, name = "abc", when = DateTime.Now });
dapper uses some knowledge of how anonymous types are implemented to understand the original order of the values, so that they are added to the command in the correct sequence (id, name, when).
One final observation:
Which means dapper is not replacing the parameter with it's given value.
Dapper never replaces parameters with their given value. That is simply not the correct way to parameterize sql: the parameters are usually sent separately, ensuring:
there is no SQL injection risk
maximum query plan re-use
no issues of formatting
Note that some ADO.NET / ODBC providers could theoretically choose to implement things internally via replacement - but that is separate to dapper.

I landed here from dublicate question: Dapper must declare the scalar variable
Error: Must declare the scalar variable "#Name".
I created queries dynamically with this piece of code:
public static bool Insert<T>(T entity)
{
var tableName = entity.GetType().CustomAttributes.FirstOrDefault(x => x.AttributeType.Name == nameof(TableAttribute))?.ConstructorArguments?.FirstOrDefault().Value as string;
if (string.IsNullOrEmpty(tableName))
throw new Exception($"Cannot save {entity.GetType().Name}. Database models should have [Table(\"tablename\")] attribute.");
DBSchema.TryGetValue(tableName.ToLower(), out var fields);
using (var con = new SqlConnection(ConnectionString))
{
con.Open();
var sql = $"INSERT INTO [{tableName}] (";
foreach (var field in fields.Where(x => x != "id"))
{
sql += $"[{field}]"+",";
}
sql = sql.TrimEnd(',');
sql += ")";
sql += " VALUES (";
foreach (var field in fields.Where(x => x != "id"))
{
sql += "#"+field + ",";
}
sql = sql.TrimEnd(',');
sql += ")";
var affectedRows = con.Execute(sql, entity);
return affectedRows > 0;
}
}
And I got the same error when my models was like this:
[Table("Users")]
public class User
{
public string Name;
public string Age;
}
I changed them to this:
[Table("Users")]
public class User
{
public string Name { get; set; }
public string Age { get; set; }
}
And it solved the problem for me.

during update query it throws NotSupportedException?

I am dealing with SQLite in windows store application.I am updating the values in table using
var tagPage = db.QueryAsync<MyModel>("UPDATE MyModel SET Tag =2 WHERE id = 1");
db.UpdateAsync(tagPage);
It throws an NotSupportedException on SQLite.cs class over the method
public int Update(object obj, Type objType)
{
if (obj == null || objType == null)
{
return 0;
}
var map = GetMapping(objType);
var pk = map.PK;
if (pk == null)
{
throw new NotSupportedException("Cannot update " + map.TableName + ": it has no PK");
}
var cols = from p in map.Columns
where p != pk
select p;
var vals = from c in cols
select c.GetValue(obj);
var ps = new List<object>(vals);
ps.Add(pk.GetValue(obj));
var q = string.Format("update \"{0}\" set {1} where {2} = ? ", map.TableName, string.Join(",", (from c in cols
select "\"" + c.Name + "\" = ? ").ToArray()), pk.Name);
return Execute(q, ps.ToArray());
}
because I think it wont get the primery key, where I have provided primery key in table.
I tried it with async and await but no use, why it is happening? please help me

Regarding your NotSupportedException issue - I suspect that your model is missing the PrimaryKey attribute:
public class MyModel
{
[PrimaryKey, AutoIncrement]
public int Id { get; set; }
public int Tag { get; set; }
public string Foo { get; set; }
}
You will need the attribute(s) above, even if your db schema already has them defined. At this time, Sqlite-Net does not read schema data from the db.
Some other thoughts:
Firstly, you should use only either the synchronous Sqlite-Net API, or the async API. Don't use both.
I personally prefer the synchronous API, as it appears to be more up to date. The async API has not been updated in 11 months, whereas the synchronous API was updated 4 months ago. Besides this I never was able to figure out how to do transactions using the async API. Again, this is personal preference.
Secondly, the Query and QueryAsync methods should be used only for querying (for SELECTs). They should not be used for UPDATEs. For adding/changing data, you will want to use these synchronous methods: Execute, Update, Insert, etc. If using the async API, there are the async counterparts (ExecuteAsync, etc).
Please read the Sqlite-Net Project page, as you will find a lot of helpful information there regarding general API usage.

Parsing SQL Statement With Irony

I am trying to create a method that converts a regular sql statement to c# objects, So i decided to use Irony to parse the sql statement then i return the statement as an Action that contains the type of the statement and the values of it depending on the type
Here is my non completed code [ Because i got frustrated as i don't know what to do then ]
private List<Action> ParseStatement(string statement)
{
var parser = new Parser(new SqlGrammar());
var parsed = parser.Parse(statement);
var status = parsed.Status;
while (parsed.Status == ParseTreeStatus.Parsing)
{
Task.Yield();
}
if (status == ParseTreeStatus.Error)
throw new ArgumentException("The statement cannot be parsed.");
ParseTreeNode parsedStmt = parsed.Root.ChildNodes[0];
switch (parsedStmt.Term.Name)
{
case "insertStmt":
var table = parsedStmt.ChildNodes.Find(x => x.Term.Name == "Id").ChildNodes[0].Token.ValueString;
var valuesCount =
parsedStmt.ChildNodes.Find(x => x.Term.Name == "insertData").ChildNodes.Find(
x => x.Term.Name == "exprList").ChildNodes.Count;
var values = parsedStmt.ChildNodes.Find(x => x.Term.Name == "insertData").ChildNodes.Find(
x => x.Term.Name == "exprList").ChildNodes;
foreach (var value in values)
{
string type = value.Token.Terminal.Name;
}
break;
}
return null;
}
private Type ParseType(string type)
{
switch (type)
{
case "number":
return typeof (int);
case "string":
return typeof (string);
}
return null;
}
So the Question Here is : How could i make use of Irony to convert a string SQL Statement to a c# objects ?
Here is an example of what i want to achieve :
INSERT INTO Persons VALUES (4,'Nilsen', 'Johan', 'Bakken 2',
'Stavanger')
And get it converted to
return new Action<string type, string table, int val1, string val2, string val3, string val4, string val5>;
Dynamically depending on what the method have read from the statement.
I hope i have well explained my idea so you can help me guys, And if there is something unclear please tell me and i will try to explain it.

I was trying to parse SQL with Irony as well. I gave up because the sample SQL parser in Irony don't handle: CTEs, Order by column number, half the special statements like
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
While I had a great time learning about Irony, I don't have the coding chops to implement all the aforementioned parts correctly.
I ended up using the Microsoft-provided SQL parsing library. Sample code for LINQPad 5 below:
// Add a reference to
// C:\Program Files (x86)\Microsoft SQL Server\130\SDK\Assemblies\
// Microsoft.SqlServer.TransactSql.ScriptDom.dll
//
// https://blogs.msdn.microsoft.com/gertd/2008/08/21/getting-to-the-crown-jewels/
public void Main()
{
var sqlFilePath = #"C:\Users\Colin\Documents\Vonigo\database-scripts\Client\Estimate\spClient_EstimateAddNew.sql";
bool fQuotedIdenfifiers = false;
var parser = new TSql100Parser(fQuotedIdenfifiers);
string inputScript = File.ReadAllText(sqlFilePath);
IList<ParseError> errors;
using (StringReader sr = new StringReader(inputScript))
{
var fragment = parser.Parse(sr, out errors);
fragment.Dump();
}
}

If you are not doing this as a fun exercise I would recommend using Linq to SQL to generate your stub classes or Entity Framework as Drunken Code Monkey mentioned in the comments.
Here's a good article to get you started: Generating EF code from existing DB

bulk insert with linq-to-sql

I have a query that looks like this:
using (MyDC TheDC = new MyDC())
{
foreach (MyObject TheObject in TheListOfMyObjects)
{
DBTable TheTable = new DBTable();
TheTable.Prop1 = TheObject.Prop1;
.....
TheDC.DBTables.InsertOnSubmit(TheTable);
}
TheDC.SubmitChanges();
}
This query basically inserts a list into the database using linq-to-sql. Now I've read online that L2S does NOT support bulk operations.
Does my query work by inserting each element at a time or all of them in one write?
Thanks for the clarification.

I modified the code from the following link to be more efficient and used it in my application. It is quite convenient because you can just put it in a partial class on top of your current autogenerated class. Instead of InsertOnSubmit add entities to a list, and instead of SubmitChanges call YourDataContext.BulkInsertAll(list).
http://www.codeproject.com/Tips/297582/Using-bulk-insert-with-your-linq-to-sql-datacontex
partial void OnCreated()
{
CommandTimeout = 5 * 60;
}
public void BulkInsertAll<T>(IEnumerable<T> entities)
{
using( var conn = new SqlConnection(Connection.ConnectionString))
{
conn.Open();
Type t = typeof(T);
var tableAttribute = (TableAttribute)t.GetCustomAttributes(
typeof(TableAttribute), false).Single();
var bulkCopy = new SqlBulkCopy(conn)
{
DestinationTableName = tableAttribute.Name
};
var properties = t.GetProperties().Where(EventTypeFilter).ToArray();
var table = new DataTable();
foreach (var property in properties)
{
Type propertyType = property.PropertyType;
if (propertyType.IsGenericType &&
propertyType.GetGenericTypeDefinition() == typeof(Nullable<>))
{
propertyType = Nullable.GetUnderlyingType(propertyType);
}
table.Columns.Add(new DataColumn(property.Name, propertyType));
}
foreach (var entity in entities)
{
table.Rows.Add(
properties.Select(
property => property.GetValue(entity, null) ?? DBNull.Value
).ToArray());
}
bulkCopy.WriteToServer(table);
}
}
private bool EventTypeFilter(System.Reflection.PropertyInfo p)
{
var attribute = Attribute.GetCustomAttribute(p,
typeof(AssociationAttribute)) as AssociationAttribute;
if (attribute == null) return true;
if (attribute.IsForeignKey == false) return true;
return false;
}

The term Bulk Insert usually refers to the SQL Server specific ultra fast bcp based SqlBulkCopy implementation. It is built on top of IRowsetFastLoad.
Linq-2-SQL does not implement insert using this mechanism, under any conditions.
If you need to bulk load data into SQL Server and need it to be fast, I would recommend hand coding using SqlBulkCopy.
Linq-2-SQL will attempt to perform some optimisations to speed up multiple inserts, however it still will fall short of many micro ORMs (even though no micro ORMs I know of implement SqlBulkCopy)

It will generate a single insert statement for every record, but will send them all to the server in a single batch and run in a single transaction.
That is what the SubmitChanges() outside the loop does.
If you moved it inside, then every iteration through the loop would go off to the server for the INSERT and run in it's own transaction.
I don't believe there is any way to fire off a SQL BULK INSERT.

LINQ Single Insert from List:
int i = 0;
foreach (IPAPM_SRVC_NTTN_NODE_MAP item in ipapmList)
{
++i;
if (i % 50 == 0)
{
ipdb.Dispose();
ipdb = null;
ipdb = new IPDB();
// .NET CORE
//ipdb.ChangeTracker.AutoDetectChangesEnabled = false;
ipdb.Configuration.AutoDetectChangesEnabled = false;
}
ipdb.IPAPM_SRVC_NTTN_NODE_MAP.Add(item);
ipdb.SaveChanges();
}

I would suggest you take a look at N.EntityFramework.Extension. It is a basic bulk extension framework for EF 6 that is available on Nuget and the source code is available on Github under MIT license.
Install-Package N.EntityFramework.Extensions
https://www.nuget.org/packages/N.EntityFramework.Extensions
Once you install it you can simply use BulkInsert() method directly on the DbContext instance. It support BulkDelete, BulkInsert, BulkMerge and more.
BulkInsert()
var dbcontext = new MyDbContext();
var orders = new List<Order>();
for(int i=0; i<10000; i++)
{
orders.Add(new Order { OrderDate = DateTime.UtcNow, TotalPrice = 2.99 });
}
dbcontext.BulkInsert(orders);