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1. Top results related to cast list example in c#

   • In C#, is it possible to cast a List to List ?

     Top Answer

     Answered Jun 16, 2020 · 67 votes

     Casting directly is not allowed because there's no way to make it typesafe. If you have a list of giraffes, and you cast it to a list of animals, you could then put a tiger into a list of giraffes! The compiler wouldn't stop you, because of course a tiger may go into a list of animals. The only place the compiler can stop you is at the unsafe conversion.

     In C# 4 we'll be supporting covariance and contravariance of SAFE interfaces and delegate types that are parameterized with reference types. See here for details:

     https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/concepts/covariance-contravariance/

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     1/5

   • Cast List to List in .NET 2.0

     Top Answer

     Answered Aug 16, 2019 · 157 votes

     .NET 2.0 has the ConvertAll method where you can pass in a converter function:

     List<int> l1 = new List<int>(new int[] { 1, 2, 3 } );List<string> l2 = l1.ConvertAll<string>(delegate(int i) { return i.ToString(); });-

     Other Answers

     Answered Mar 02, 2010 · 125 votes

     Updated for 2010

     List<int> l1 = new List<int>(new int[] { 1,2,3 } );List<string> l2 = l1.ConvertAll<string>(x => x.ToString());-

     Other Answers

     Answered Sep 06, 2022 · 8 votes

     Is C# 2.0 able to do List<T>.Convert? If so, I think your best guess would be to use that with a delegate:

     List<int> list = new List<int>();list.Add(1);list.Add(2);list.Add(3);list.Convert(delegate (int i) { return i.ToString(); });-

     Something along those lines.

     Glenn's answer is probably the correct code ;-)

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     2/5

   • Example of MPXJ library in C#

     Top Answer

     Answered Dec 16, 2010 · 5 votes

     hopefully this will help.

     First you need to open your project file:

     ProjectReader reader = ProjectReaderUtility.getProjectReader(inputFile);ProjectFile projectFile = reader.read(inputFile);-

     This assumes that you have a file name in the inputFile string.

     The method below should be treated as pseudocode (i.e. I haven't compiled it, shaken the bugs out of it and so on, and it's not the most elegant thing I've ever written), but it illustrates the approach:

     public void dumpTables(ProjectFile file){ List tables = file.getTables(); Iterator iter = tables.iterator(); while (iter.hasNext()) { Table table = (Table)iter.next(); if (table.getResourceFlag()) { List resources = file.getAllResources(); Iterator resourceIter = resources.iterator(); while (resourceIter.hasNext()) { Resource resource = (Resource)iter.next(); List columns = table.getColumns(); Iterator columnIter = columns.iterator(); while (columnIter.hasNext()) { Column column = (Column)columnIter.next(); Object columnValue = resource.getCachedValue(column.getFieldType()); Console.Write(columnValue); Console.Write(","); } Console.WriteLine(); } } else { List tasks = file.getAllTasks(); // etc. as above } }}

     The idea is that you are retrieving the list of tables present in the file, and for each one working out if it is a Task or Resource table. Based on this you'll grab the list of tasks or resources, iterate through that, and for each instance pull out the column value and display it. Note that I've not made any attempt to order the tasks or resources in any particular way. I'll leave that as an exercise for the reader!

     Hope that helps!

     Jon

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     3/5

   • Example of array.map() in C#?

     Top Answer

     Answered May 20, 2020 · 189 votes

     This is called projection which is called Select in LINQ. That does not return a new array (like how JavaScript's .map does), but an IEnumerable<T>. You can convert it to an array with .ToArray.

     using System.Linq; // Make 'Select' extension available...var ages = people.Select(person => person.Age).ToArray();

     Select works with all IEnumerable<T> which arrays implement. You just need .NET 3.5 and a using System.Linq; statement.

     For your 2nd example use something like this. Notice there are no arrays in use - only sequences.

     var items = Enumerable.Range(1, 4).Select(num => string.Format("{0}a", num));-

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     4/5

   • Cast error in C#

     Top Answer

     Answered Mar 19, 2013 · 3 votes

     The reason may be you are getting null values. So you ca create an extension method as follows

     public static T ExecuteNullableScalar<T>(this SqlCommand cmd) where T : struct{ var result = cmd.ExecuteScalar(); if (result == DBNull.Value) return default(T); return (T)result;}

     Usage becomes:

     int value = cmd.ExecuteNullableScalar<int>();//new approachulong value=cmd.ExecuteNullableScalar<ulong>();-

     Other-Wise

     myConnection.Open(); var o = cmd.ExecuteScalar(); OrderID = (o== DBNull.Value ? 0 : Convert.ToUInt64(o)); myConnection.Close();

     changed

     OrderID = (o== DBNull.Value ? 0 : Convert.ToUInt64(o));-

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     5/5

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2. stackoverflow.com › questions › 504729c# - How do I cast a List<T> effectively? - Stack Overflow

   stackoverflow.com › questions › 504729

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   Mar 4, 2009 · 49. Both .OfType<T> and .Cast<T> will return a list of T, but the meaning of the two methods is different. list.OfType () filters the original list and returns all items which are of type T, and skips the ones that are not of that type. list.Cast () casts all items in the original list to type T, and throws an exception for items which cannot ...

3. learn.microsoft.com › en-us › dotnetEnumerable.Cast<TResult>(IEnumerable) Method (System.Linq)

   learn.microsoft.com › en-us › dotnet

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   • Definition
   • Examples
   • Remarks
   • See also

   Namespace:\tSystem.Linq

   Assembly:\tSystem.Linq.dll

   Assembly:\tSystem.Core.dll

   Assembly:\tnetstandard.dll

   Casts the elements of an IEnumerable to the specified type. Public Function Cast(Of TResult) (source As IEnumerable) As IEnumerable(Of TResult) Type Parameters

   TResult

   See full list on learn.microsoft.com

   The following code example demonstrates how to use Cast (IEnumerable) to enable the use of the standard query operators on an ArrayList.

   See full list on learn.microsoft.com

   This method is implemented by using deferred execution. The immediate return value is an object that stores all the information that is required to perform the action. The query represented by this method is not executed until the object is enumerated either by calling its GetEnumerator method directly or by using foreach in C# or For Each in Visual Basic.

   The Cast (IEnumerable) method enables the standard query operators to be invoked on non-generic collections by supplying the necessary type information. For example, ArrayList does not implement IEnumerable , but by calling Cast (IEnumerable) on the ArrayList object, the standard query operators can then be used to query the sequence.

   If an element cannot be converted to type TResult, this method throws a InvalidCastException.

   The source sequence for this method is IEnumerable, which means the elements have the compile-time static type of object. The only type conversions that are performed by this method are reference conversions and unboxing conversions. The runtime type of the elements in the collection must match the target type, or in the case of value types, the runtime type of elements must be the result of a boxing conversion of the target type. Other conversion types, such as those between different numeric types, are not allowed.

   To obtain only those elements that can be converted to type TResult, use the OfType method instead of Cast (IEnumerable).

   In a query expression, an explicitly typed iteration variable translates to an invocation of Cast (IEnumerable). This example shows the syntax for an explicitly typed range variable. Use the select clause of a query to perform other conversion types, like the implicit numeric conversions. The following example uses both the Cast method and a select statement to convert a sequence of boxed integers to a sequence of doubles.

   See full list on learn.microsoft.com

   •from clause (C# Reference)

   •From Clause (Visual Basic)

   See full list on learn.microsoft.com

4. People also ask

   What is the difference between list of type and list cast?

   • list.OfType () filters the original list and returns all items which are of type T, and skips the ones that are not of that type. list.Cast () casts all items in the original list to type T, and throws an exception for items which cannot be cast to that type.

   c# - How do I cast a List effectively? - Stack Overflow

   stackoverflow.com/questions/504729/how-do-i-cast-a-listt-effectively

   See all results for this question

   Is it possible to cast a list from one type to another?

   • I know it's possible to cast a list of items from one type to another (given that your object has a public static explicit operator method to do the casting) one at a time as follows: ListOfY.Add((Y)x); But is it not possible to cast the entire list at one time? For example,

   Shorter syntax for casting from a List to a List ?

   stackoverflow.com/questions/5115275/shorter-syntax-for-casting-from-a-listx-to-a-listy

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   Does a cast change the run-time type of a reference?

   • A cast operation between reference types doesn't change the run-time type of the underlying object; it only changes the type of the value that is being used as a reference to that object. For more information, see Polymorphism. In some reference type conversions, the compiler can't determine whether a cast is valid.

   Casting and type conversions - C# Programming Guide - C#

   learn.microsoft.com/en-us/dotnet/csharp/programming-guide/types/casting-and-type-conversions

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   Why can't I make a cast in C#?

   • You cannot make your desired cast because, as others have written, collections in c# are not covariant. You can either create a new list, or introduce a ListWrapper class like so:

   .net - C# Cast List of MyType to List of objects - Stack Overflow

   stackoverflow.com/questions/24356083/c-sharp-cast-list-of-mytype-to-list-of-objects

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5. dotnettutorials.net › lesson › cast-operatorLINQ Cast Method in C# with Examples - Dot Net Tutorials

   dotnettutorials.net › lesson › cast-operator

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   The LINQ Cast method in C# is used to cast elements of a non-generic collection to a specified type. It’s a part of the System.Linq namespace can be applied to any type that implements IEnumerable, converting it into an IEnumerable<T> where T is the target type. The Cast method is particularly useful when working with not strongly typed ...

6. stackoverflow.com › questions › 24356083.net - C# Cast List of MyType to List of objects - Stack Overflow

   stackoverflow.com › questions › 24356083

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   Jun 23, 2014 · Cast List of MyType to List of objects. As @Charles said, IList<T> and List<T> are not variant, so you can't cast IList<DerivedClass> to IList<BaseClass>. You have to create new List<BaseClass>. There are many ways to do that, I think there are two you should consider: You can use Cast and ToList, but it will require using System.Linq.

7. learn.microsoft.com › en-us › dotnetCasting and type conversions - C# Programming Guide - C#

   learn.microsoft.com › en-us › dotnet

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   Mar 19, 2024 · C# provides the is operator to enable you to test for compatibility before actually performing a cast. For more information, see How to safely cast using pattern matching and the as and is operators. C# language specification. For more information, see the Conversions section of the C# language specification. See also. Types; Cast expression

8. www.codingame.com › castCast - Using C# LINQ - A Practical Overview - CodinGame

   www.codingame.com › cast

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   The Cast<U>() method casts each element of a source IEnumerable<T> sequence, individually, to a base or derived type U and returns a sequence containing all of the resultant elements. NOTE: If the source type T can't be cast to the result type U then the cast will fail with an InvalidCastException. IEnumerable<IComparable> values = new List ...

9. www.dotnetperls.com › castC# Cast Examples - Dot Net Perls

   www.dotnetperls.com › cast

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   Nov 1, 2023 · Casts. In C# code a set of complex rules resolves casts. In some cases data is lost and the cast cannot be reversed. In others an exception is provoked.