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LINQ Select Many statement


LINQ Select Many statement

By : user2950311
Date : November 17 2020, 11:52 AM
Any of those help From MSDN Linq operators article I found below statement. I , No, that query is equivelant to this:
code :
foreach(var c in customers)
{
    foreach(var o in c.Orders)
    {
        if(o.Total >= 2000.0M)
           yield return new { c.CustomerID, o.OrderID, o.Total }; 
    }
}


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LINQ Select Statement

LINQ Select Statement


By : cgddrd
Date : March 29 2020, 07:55 AM
To fix this issue I'm developing a web application myself to follow some rssfeeds. My purpose is just learning some ajax and i send data from server to client side in JSON format. I use LINQ for querying data and JSON .NET API for object to string Serialization in the server side. The problem is that because of there exists foreign keys between my tables linq objects include references to the same table and JSON .NET API throws self referencing object error. , problem solved.
code :
p.RSSFeeds.Select(x => new {x.Description,x.RSSFeedID}),
LINQ: How do I perform an inline select statement in a LINQ statement?

LINQ: How do I perform an inline select statement in a LINQ statement?


By : morpheusIsMe
Date : March 29 2020, 07:55 AM
To fix this issue I have the following SQL: , You can write Select L, L.UrlHistory.Count()
Select values in anonymous type with func in linq select statement

Select values in anonymous type with func in linq select statement


By : Pompilia Buzatu
Date : March 29 2020, 07:55 AM
I hope this helps . Your problem can be expressed much more simply, eg this reproduces it:
code :
Func<SomeClass, int> x = t => t.ID;
var y = db.SomeClasses.Select(c => x(c)).ToArray();
Expression<Func<SomeClass, int>> x = t => t.ID;
var y = db.SomeClasses.Select(x).ToArray();
Func<SomeClass, int> x = t => t.ID;
var y = db.SomeClasses.AsEnumerable().Select(c => x(c)).ToArray();
Have EF Linq Select statement Select a constant or a function

Have EF Linq Select statement Select a constant or a function


By : Syed Waqar
Date : March 29 2020, 07:55 AM
should help you out It would technically be possible to pass the Expression in your Select query through an expression tree visitor, which checks for constant values on the left-hand side of ternary operators, and replaces the ternary expression with the appropriate sub-expression.
For example:
code :
public class Simplifier : ExpressionVisitor
{
    public static Expression<T> Simplify<T>(Expression<T> expr)
    {
        return (Expression<T>) new Simplifier().Visit(expr);
    }

    protected override Expression VisitConditional(ConditionalExpression node)
    {
        var test = Visit(node.Test);
        var ifTrue = Visit(node.IfTrue);
        var ifFalse = Visit(node.IfFalse);

        var testConst = test as ConstantExpression;
        if(testConst != null)
        {
            var value = (bool) testConst.Value;
            return value ? ifTrue : ifFalse;
        }

        return Expression.Condition(test, ifTrue, ifFalse);
    }

    protected override Expression VisitMember(MemberExpression node)
    {
        // Closed-over variables are represented as field accesses to fields on a constant object.
        var field = (node.Member as FieldInfo);
        var closure = (node.Expression as ConstantExpression);
        if(closure != null)
        {
            var value = field.GetValue(closure.Value);
            return VisitConstant(Expression.Constant(value));
        }
        return base.VisitMember(node);
    }
}
void Main()
{
    var b = true;
    Expression<Func<int, object>> expr = i => b ? i.ToString() : "N/A";
    Console.WriteLine(expr.ToString()); // i => IIF(value(UserQuery+<>c__DisplayClass0).b, i.ToString(), "N/A")
    Console.WriteLine(Simplifier.Simplify(expr).ToString()); // i => i.ToString()
    b = false;
    Console.WriteLine(Simplifier.Simplify(expr).ToString()); // i => "N/A"
}
Expression<Func<IGrouping<DateTime, MyEntity>>, ClassYouWantToReturn> select = 
    groupedDate => new {
        Calculation1 = doCalculation1 ? x.Sum(groupedDate.Column1) : 0),
        Calculation2 = doCalculation2 ? x.Count(groupedDate) : 0
    };
var q = dbEntity
    .GroupBy(x => x.date)
    .Select(Simplifier.Simplify(select))
How do I select individual fields in a Dynamic LINQ Select Statement?

How do I select individual fields in a Dynamic LINQ Select Statement?


By : simon
Date : March 29 2020, 07:55 AM
this will help I figured it out. This is the format in which it wanted the fields described as:
code :
Dim data = both.Select("new (row1[0] as Account))
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