I am using SubSonic 3.0.0.3 along with the Linq T4 Templates. My ProjectRepository, for example, has the following two methods:
public int Add(Project item)
{
int result = 0;
ISqlQuery query = BuildInsertQuery(item);
if (query != null)
{
result = query.Execute();
}
return result;
}
private ISqlQuery BuildInsertQuery(Project item)
{
ITable tbl = FindTableByClassName();
Insert query = null;
if (tbl != null)
{
Dictionary<string, object> hashed = item.ToDictionary();
query = new Insert(_db.Provider).Into<Project>(tbl);
foreach (string key in hashed.Keys)
{
IColumn col = tbl.GetColumn(key);
if (col != null)
{
if (!col.AutoIncrement)
{
query.Value(key, hashed[key]);
}
}
}
}
return query;
}
Along with performing the insert (which works great), I'd really like to get the value of the auto-incrementing ProjectId column. For the record, this column is both the primary key and identity column. Is there perhaps a way to append "SELECT SCOPE_IDENTITY();" to the query or maybe there's an entirely different approach which I should try?
You can do this with the ActiveRecord templates which does all of the wiring above for you (and also has built-in testing). In your scenario, the Add method would have one line: Project.Add() and it would return the new id.
For your needs, you can try this:
var cmd=query.GetCommand();
cmd.CommandSql+=";SELECT SCOPE_IDENTITY() as newid";
var newID=query.Provider.ExecuteScalar(cmd);
That should work..
*Edit - you can create an ExtensionMethod for this on ISqlQuery too, to save some writing...
Related
In my C# application i am using linq. I need a help what is the syntax for if-elseif- using linq in single line. Data, RangeDate are the inputs. Here is the code:
var Date1 = RangeData.ToList();
int record =0;
foreach (var tr in Date1)
{
int id =0;
if (tr.Item1 != null && tr.Item1.port != null)
{
id = tr.Item1.port.id;
}
else if (tr.Item2 != null && tr.Item2.port != null)
{
id = tr.Item2.port.id;
}
if (id >0)
{
if(Data.Trygetvalue(id, out cdat)
{
// Do some operation. (var cdata = SumData(id, tr.item2.port.Date)
record ++;
}
}
}
I think your code example is false, your record variable is initialized to 0 on each loop so increment it is useless .
I suppose that you want to count records in your list which have an id, you can achieve this with one single Count() :
var record = Date1.Count(o => (o.Item1?.port?.id ?? o.Item2?.port?.id) > 0);
You can use following code:
var count = RangeData.Select(x => new { Id = x.Item1?.port?.id ?? x.Item2?.port?.id ?? 0, Item = x })
.Count(x =>
{
int? cdate = null; // change int to your desired type over here
if (x.Id > 0 && Data.Trygetvalue(x.Id, out cdat))
{
// Do some operation. (var cdata = SumData(x.Id, x.Item.Item2.port.Date)
return true;
}
return false;
});
Edit:
#D Stanley is completely right, LINQ is wrong tool over here. You can refactor few bits of your code though:
var Date1 = RangeData.ToList();
int record =0;
foreach (var tr in Date1)
{
int? cdat = null; // change int to your desired type over here
int id = tr.Item1?.port?.id ?? tr.Item2?.port?.id ?? 0;
if (id >0 && Data.Trygetvalue(id, out cdat))
{
// Do some operation. (var cdata = SumData(id, tr.Item2.port.Date)
record ++;
}
}
Linq is not the right tool here. Linq is for converting or querying a collection. You are looping over a collection and "doing some operation". Depending on what that operation is, trying to shoehorn it into a Linq statement will be harder to understand to an outside reader, difficult to debug, and hard to maintain.
There is absolutely nothing wrong with the loop that you have. As you can tell from the other answers, it's difficult to wedge all of the information you have into a "single-line" statement just to use Linq.
public static object ExecuteScalar(string SQL)
{
try
{
var A = new EGModel.EGEntity().Connection;
var command = ((EntityConnection)(A)).StoreConnection.CreateCommand();
command.CommandType = System.Data.CommandType.Text;
command.CommandText = SQL;
if (((EntityConnection)(A)).StoreConnection.State == System.Data.ConnectionState.Closed)
((EntityConnection)(A)).StoreConnection.Open();
return command.ExecuteScalar();
}
catch { return null; }
}
public object MFICHE(int ID)
{
var i = from b in IConnection.EGEntity().fiche
where (m.ID== ID)
select new { b.Date, m.Name, Addresss = IConnection.ExecuteScalar("SELECT main.F_ADDRESS(4588)") };
return i;
}
I am getting error:
LINQ to Entities does not recognize the method 'System.Object ExecuteScalar(System.String)' method, and this method cannot be translated into a store expression.
Why i am getting error?
But Addresss = "ASASAS" is runing?
The problem is that the expression tree generated from your query includes a call to your ExecuteScalar method - which the Entity Framework expression parser doesn't know anything about. It doesn't look inside that method to see what it's doing - it just knows that the call exists, and fails because it can't translate it.
You wouldn't normally want to execute a separate SQL statement for each result returned from a query? You've got an obvious "N+1 selects" problem.
If you know you've only got a single result (due to the ID constraint) you could fetch the relevant data into an object and then execute the second query:
public object MFICHE(int ID)
{
var query = from b in IConnection.EGEntity().fiche
where b.ID == ID
select new { b.Date, b.Name };
// You only expect a single result, right?
var result = query.Single();
// Shouldn't this be using something to do with the result?
var address = IConnection.ExecuteScalar("SELECT main.F_ADDRESS(4588)");
return new { result.Date, result.Name, Address = address };
}
As an aside, it's very odd to have static methods in a type beginning with I, which would usually be an interface. Additionally, this code:
catch { return null; }
is horrible - you should catch specific exceptions, log them, and normally rethrow them. It's almost never appropriate to just carry on as if nothing had gone wrong.
While looking though some code of the project I'm working on, I've come across a pretty hefty method which does
the following:
public string DataField(int id, string fieldName)
{
var data = _dataRepository.Find(id);
if (data != null)
{
if (data.A == null)
{
data.A = fieldName;
_dataRepository.InsertOrUpdate(data);
return "A";
}
if (data.B == null)
{
data.B = fieldName;
_dataRepository.InsertOrUpdate(data);
return "B";
}
// keep going data.C through data.Z doing the exact same code
}
}
Obviously having 26 if statements just to determine if a property is null and then to update that property and do a database call is
probably very naive in implementation. What would be a better way of doing this unit of work?
Thankfully C# is able to inspect and assign class members dynamically, so one option would be to create a map list and iterate over that.
public string DataField(int id, string fieldName)
{
var data = _dataRepository.Find(id);
List<string> props = new List<string>();
props.Add("A");
props.Add("B");
props.Add("C");
if (data != null)
{
Type t = typeof(data).GetType();
foreach (String entry in props) {
PropertyInfo pi = t.GetProperty(entry);
if (pi.GetValue(data) == null) {
pi.SetValue(data, fieldName);
_dataRepository.InsertOrUpdate(data);
return entry;
}
}
}
}
You could just loop through all the character from 'A' to 'Z'. It gets difficult because you want to access an attribute of your 'data' object with the corresponding name, but that should (as far as I know) be possible through the C# reflection functionality.
While you get rid of the consecutive if-statements this still won't make your code nice :P
there is a fancy linq solution for your problem using reflection:
but as it was said before: your datastructure is not very well thought through
public String DataField(int id, string fieldName)
{
var data = new { Z = "test", B="asd"};
Type p = data.GetType();
var value = (from System.Reflection.PropertyInfo fi
in p.GetProperties().OrderBy((fi) => fi.Name)
where fi.Name.Length == 1 && fi.GetValue(data, null) != null
select fi.Name).FirstOrDefault();
return value;
}
ta taaaaaaaaa
like that you get the property but the update is not yet done.
var data = _dataRepository.Find(id);
If possible, you should use another DataType without those 26 properties. That new DataType should have 1 property and the Find method should return an instance of that new DataType; then, you could get rid of the 26 if in a more natural way.
To return "A", "B" ... "Z", you could use this:
return (char)65; //In this example this si an "A"
And work with some transformation from data.Value to a number between 65 and 90 (A to Z).
Since you always set the lowest alphabet field first and return, you can use an additional field in your class that tracks the first available field. For example, this can be an integer lowest_alphabet_unset and you'd update it whenever you set data.{X}:
Init:
lowest_alphabet_unset = 0;
In DataField:
lowest_alphabet_unset ++;
switch (lowest_alphabet_unset) {
case 1:
/* A is free */
/* do something */
return 'A';
[...]
case 7:
/* A through F taken */
data.G = fieldName;
_dataRepository.InsertOrUpdate(data);
return 'G';
[...]
}
N.B. -- do not use, if data is object rather that structure.
what comes to my mind is that, if A-Z are all same type, then you could theoretically access memory directly to check for non null values.
start = &data;
for (i = 0; i < 26; i++){
if ((typeof_elem) *(start + sizeof(elem)*i) != null){
*(start + sizeof(elem)*i) = fieldName;
return (char) (65 + i);
}
}
not tested but to give an idea ;)
I have an array-list that contains some UserID.
I need a query like this:
vat tmp= users.select(a=> a.UserID in (arraylist));
what can I do?
If it's actually in an ArrayList, you should create a List<T> or array first. Then you can use Contains:
// Use the appropriate type, of course.
var ids = arraylist.Cast<string>().ToList();
var tmp = users.Select(a => ids.Contains(a.UserID));
While using Contains on the plain ArrayList may well compile, I would expect it to fail at execution time, assuming users is an IQueryable<>.
List<long> list =new List<long>();
var selected = from n in users where list.Contains(n.ID) select n ;
OR
var selected = users.Where(a=> list.Contains(a.ID)).ToList();
This is the solution I used.
public static IEnumerable<SettingModel> GetSettingBySettingKeys(params string[] settingKey)
{
using (var db = new BoxCoreModelEntities())
{
foreach (var key in settingKey)
{
var key1 = key;
yield return Map(db.Settings.Where(s => s.SettingKey == key1).First());
}
}
}
I'm iterating the tables of a context and then the properties of those tables to eager load all columns in a context. I received some help via another question, but I don't seem to be able to figure out how to iterate the column properties of the actual table.
Final working code:
public static void DisableLazyLoading(this DataContext context)
{
DataLoadOptions options = new DataLoadOptions();
var contextTables = context.GetType().GetProperties().Where(n => n.PropertyType.Name == "Table`1");
foreach (var contextTable in contextTables)
{
var tableType = contextTable.GetValue(context, null).GetType().GetGenericArguments()[0];
var tableProperties = tableType.GetProperties().Where(n => n.PropertyType.Name != "EntitySet`1");
foreach (var tableProperty in tableProperties)
{
ParameterExpression paramExp = Expression.Parameter(tableType, "s");
Expression expr = Expression.Property(paramExp, tableProperty.Name);
options.LoadWith(Expression.Lambda(expr, paramExp));
}
}
context.LoadOptions = options;
}
You're only getting the ProperInfos. You need to get the values from the PropertyInfos:
var tablePropertInfos = context.GetType().GetProperties().Where(
n => n.PropertyType.Name == "Table`1");
foreach (var tablePropertyInfo in tablePropertInfos)
{
// Get the actual table
var table = tablePropertyInfo.GetValue(context, null);
// Do the same for the actual table properties
}
Once you have the PropertyInfo class, you need to get the value using the GetValue method.