I would like to convert a list of User's properties into strings array (for json receiver) like:
List<User> users = <..list of users from db...>
var jsonData = (
from user in users
select new { user.Id, user.Person.Lastname, user.Person.Firstname });
return Json(jsonData)
The result is an array named fields
[{"Id":1,"Lastname":"Doe","Firstname":"John"},{"Id":2,"Lastname":"Smith","Firstname":"Adam"},...]
but I would like it to be the array of arrays of plain strings like:
[["1","Doe","John"]
["2","Smith","Adam"], ...]
How to cast linq result to strings array?
var jsonData = from user in users
select new[] { user.Id.ToString(),
user.Person.Lastname,
user.Person.Firstname };
Alternatively, you can use the lambda syntax:
var jsonData = users.Select(user => new[] { user.Id.ToString(),
user.Person.Lastname,
user.Person.Firstname });
I was using an IQueryable as the starting point of creating an array of values, not a List<>, but in either case you can serialise an anonymous object array, instead of a string array, to get the same result without casting values to strings.:
e.g.
var jsonData = users.Select(user => new object[] {
user.Id,
user.Person.Lastname,
user.Person.Firstname
});
In my instance I was also using the result client-side with jQuery dataTable, so the result needed to be wrapped in another anonymous object (with the property name aadata).
e.g.
return Json(new { aaData = jsonData }, JsonRequestbehavior.AllowGet);
Hopefully this will help others that find this question looking for dataTable specific version of this problem (as I was).
Related
I need to return a number of Linq query results into a List object based on a foreign key value. What is the syntax for doing this? I am new to using Linq, so below is my best guess so far. I receive an error in the .Where() "clause" stating "The name 'pt' does not exist in the current context. Any help would be greatly appreciated!
List<AgentProductTraining> productTraining = new List<AgentProductTraining>();
var prodCodes = productTraining.Select(pt => new[]
{
pt.ProductCode,
pt.NoteId,
pt.ControlId
})
.Where(pt.CourseCode == course.CourseCode);
You would need to switch the locations of where and select if you're using extension methods:
var prodCodes = productTraining.Where(pt => pt.CourseCode == course.CourseCode)
.Select(pt => new SomeRandomType
{
ProductCode = pt.ProductCode,
NoteId = pt.NoteId,
ControlId = pt.ControlId
});
I also recommend, as you can see above, that you create a type for that select statement so that you're not relying on anonymous types. You should put in into an object type that you know everything about.
Also, if CourseCode is a string, that should be pt.CourseCode.Equals(course.CourseCode).
I am trying to replace a string date value "01/01/1700" with an empty string in LINQ.
The date is of type string.
Something like this but I cant get it to work.
Query<Client>(sql).ToList().ForEach(x => x.DateOfBirth =
x.DateOfBirth.Replace("01/01/1700", ""));
This code works but its not LINQ.
var result = Query<Client>(sql).ToList();
foreach (var client in result)
{
if (client.DateOfBirth == "01/01/1700")
{
client.DateOfBirth = "n/a";
}
}
Thanks for your help.
The problem is the ToList(). The result is not visible in the variable you use afterwards.
Try out the following:
var list = Query<Client>(sql).ToList();
list.ForEach(l => l.DateOfBirth = l.DateOfBirth.Replace("01/01/1700", "n/a"));
Should work fine. Use the list variable afterwards.
var result = Query<Client>(sql).ToList();
result.ForEach(l => l.DateOfBirth = l.DateOfBirth.Replace("01/01/1700", "n/a"));
Your code assumes that changes made to an object in a List will be reflected in the Query<Client> that the object came from. Apparently this is not the case. One thing you could try is assigning the list before calling ForEach() and using the list from that point on:
var clients = Query<Client>(sql).ToList();
clients.ForEach(x => x.DateOfBirth = x.DateOfBirth.Replace("01/01/1700", ""));
Also, ForEach is not a LINQ operator. It is a method in the List class. Unlike LINQ operators, it will modify the list that called it and will not return anything. The way to "modify" data with LINQ is by using select:
var clients = (from client in Query<Client>(sql).ToList()
select new Client(client)
{
DateOfBirth = client.DateOfBirth.Replace("01/01/1700", "")
}).ToList();
I'm breaking my head with this and decided to share my problem with you
I want to create an anonymous select from several tables, some of them may contain more than one result. i want to concatenate these results into one string
i did something like this:
var resultTable = from item in dc.table
select new
{
id= item.id,
name= CreateString((from name in item.Ref_Items_Names
select name.Name).ToList()),
};
and the CreateString() is:
private string CreateString(List<string> list)
{
StringBuilder stringedData = new StringBuilder();
for (int i = 0; i < list.Count; i++)
{
stringedData.Append(list[i] + ", ");
}
return stringedData.ToString();
}
my intentions were to convert the "name" query to list and then sent it to CreateString() to convert it to one long concatenated string.
I tried using .Aggregate((current,next) => current + "," + next);
but when i try to convert my query to DataTable like below:
public DataTable ToDataTable(Object query)
{
DataTable dt = new DataTable();
IDbCommand cmd = dc.GetCommand(query as IQueryable);
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = (SqlCommand)cmd;
cmd.Connection.Open();
adapter.Fill(dt);
cmd.Connection.Close();
return dt;
}
I'm getting exception that "dc.GetCommand()" can't understand query with Aggregate method
later I tried to even use this simple query:
var resultTable = from itemin dc.table
select new
{
name = CreateString()
};
When CreateString() returns "success", nothing was inserted to "name"
why there is no way of using methods in select clause?
Thank you
Yotam
There is difference between LINQ to objects and LINQ to some-db-provider. Generally speaking, when using IQueryable, you can't use any methods, except the ones your provider understands.
What you can do is to retrieve the data from the database and then do the formatting using LINQ to objects:
var data = from item in dc.table
where /* some condition */
select item;
var result = from item in data.AsEnumerable()
select new
{
name = SomeFunction(item)
}
The AsEnumerable() extension method forces processing using LINQ to objects.
Forgive me if I've miss interpreted your question. It seems that what you are trying to do is abstract your select method for reuse. If this is the case, you may consider projection using a lambda expression. For example:
internal static class MyProjectors
{
internal static Expression<Func<Object1, ReturnObject>> StringDataProjector
{
get
{
return d => new Object1()
{
//assignment here
}
}
}
}
Now you can select your datasets as such:
dc.Table.Select(MyProjectors.StringDataProjector)
As for the concatenation logic, what about selecting to some base class with an IEnumerable<string> property and a read-only property to handle the concatenation of the string?
I am trying to access an object with form data sent to my controller. However, when I try to access objects I get values of null or 0. I used two methods, the first by serializing and the second by storing names and values in one object. (the code below sends/posts serialized)
Here is my JS...
$("#createUser").click(function() {
//store input values
var inputs = $('#newUserForm :input');
var input = $('#newUserForm :input').serializeArray();
console.log(input);
//if I want just the values in one object
var values = {};
$(inputs).each(function() {
values[this.name] = $(this).val();
});
console.log(values);
if(LiveValidation.massValidate( validObj )){
$.post('./adminPanel/createUser', function(input){
alert('Load was performed.');
//test confirmation box
$("#msgbox").html("Grrrrreat");
//drop down confirmation
$("#msgbox").slideDown();
});
} else {
//test fail box
$("#failbox").html("Fail");
$("#failbox").slideDown();
}
});
In the controller side I try to access data the following way...
$this->input->post("firstName")
where firstName is the name of the field.
Below is an image of the objects passed.
Top being serialized array and the bottom a single object with all the names and values of form...
If you're using jQuery, you can use jQuery's built in serialize/query string functions to get the data from a form: http://api.jquery.com/serialize/
In your case:
var data = $('#newUserForm').serialize(); // is a string like "firstName=jon"
I have a function inside a class that will run a Linq to Entities query (or any type of Linq query actually), and it's gonna return 2 columns in the resultset. I would like to return an object to whoever is calling my function that will allow Intellisense to know what I have returned.
Let me explain. If I have a function like this:
public static IQueryable GetInfo(MyEntityModel oEntityModel)
{
var query =
(from t in oEntityModel.Table1
from u in t.Table2
where t.Status == true &&
u.Status == true
select new
{
t.Column1,
u.Column2
})
return query;
}
What can (should) I put instead of IQueryable so that whoever calls my GetInfo function, will get Intellisense from the resultset, and show that it has a Column1 and Column2?
var linqresult = ClsLinqTeste.GetInfo(oEntityModel);
if (linqresult.Column1 == 1)
{
foreach (var oItem in linqresult)
{
.. do stuff...
}
}
Tks
You cannot return an anonymous type from a function, they are strictly "inline" classes. When you return it, the foreach loop will only be able to interpret the result as an plain object. I guess you could use reflection to query the property names and values, however it seems much more straight forward to define a data transfer type to hold the results.
See this question, and this blog post.
So you could create a simple struct or class:
public class MyDataResult
{
public object Column1 { get; set; }
public object Column2 { get; set; }
}
Then modify your query in the function:
public static IQueryable<MyDataResult> GetInfo(MyEntityModel oEntityModel)
{
var query =
(from t in oEntityModel.Table1
from u in t.Table2
where t.Status == true &&
u.Status == true
select new MyDataResult
{
Column1 = t.Column1,
Column2 = u.Column2
})
return query;
}
Something like that should work. Note that I used "object" for the properties in MyDataResult. I don't know the types of the columns you are returning, you should use the actual types in order to get full intellisense.
You are returning a collection of anonymous types, they will be casted to objects, so when you try to iterate over them, altough they will be your objects (and they will contain your properties) at compile time they will be casted to objects:
foreach (var x in ClsLinqTeste.GetInfo(oEntityModel))
{
//x is an Object
}
You can read more about it here.
If you want to have intellisense, I suggest you create a custom class they will hold your properties and return not an anonymous type (using new {}) but object of your class (new MyClass(prop1, prop2)). You also need to change signature of your method, so it returns IQueryable<YourClass> and not just plain non-generic IQueryable.
As others have said, creating a new type to hold the two columns is usually the best option.
But if, for some reason, you don't want to do that and you are using .Net 4.0, you can use Tuple:
public static IQueryable<Tuple<Column1Type, Column2Type>>
GetInfo(MyEntityModel oEntityModel)
{
return from …
select Tuple.Create(t.Column1, u.Column2);
}
var linqresult = ClsLinqTeste.GetInfo(oEntityModel);
foreach (var oItem in linqresult)
Console.WriteLIne(oItem.Item1, oItem.Item2);
When you return your resultset AsQueryable, the app is already able to give you intellisense, however in your example, you must specify either .FirstOrDefault if you know your collection will only have a single row, or iterate over your collection to get the items from it, like so:
This is what you're doing:
var linqresult = ClsLinqTeste.GetInfo(oEntityModel);
if (linqresult.Column1 == 1)
{
..do stuff...
}
This is how you should do it:
var linqresult = ClsLinqTeste.GetInfo(oEntityModel);
foreach(var item in linqresult)
{
if (item.Column1 == 1)
{
..do stuff...
}
}
You must iterate over linqresult because when you query with link, it returns a result set, even if it just has one column. As with any collection, your data columns aren't available on the whole result set, only with individual items.
If you want to strongly typed enumerate a non-generic IEnumerable (IEnumerable.GetEnumerator() instead of IEnumerable<T>.GetEnumerator<T>()) you can use the Cast<>() extension, like so
var myquery = GetQueryable();
for (var item in myquery.Cast<MyDataType>())
{
// use item.Column1 directly and strongly typed with intellisense
}