How to restrict T to value types using a constraint?

class type constraint
the type t must be a reference type
generic method with multiple type parameters c#
t is a type parameter', which is not valid
c# new() constraint with parameters
c# generic constraint primitive type
c# generic nullable constraint
c# where t is nullable

I want to restrict the possible types N can take-on using a constraint. I wish to restrict N to be either a int or a decimal.

public static Chart PopulateInto<T, N>(List<T> yAxis, List<N> xAxis) where N : int, decimal
{
    // Do stuff here
}

Any help appreciated...

Constraints on type parameters, For information about nullable value types, see Nullable value types. You can't combine the struct constraint with the unmanaged constraint. When applying the where T : class constraint, avoid the == and != operators on the type parameter because these operators will test for reference identity only, not for value equality. This behavior occurs even if these operators are overloaded in a type that is used as an argument.

It's not possible to constrain a generic parameter to a specific value type.

You can however force it to be a value type or struct by adding where N : struct, but that's all.

where (generic type constraint), public class AGenericClass<T> where T : IComparable<T> { } To allow nullable reference types, use the class? constraint, which allows both nullable and That type may be a value type or a non-nullable reference type. This is pretty cool, but would it be possible to modify this solution to make the methods accept some generic type T that is or inherits from the various IntX classes? I like this solution because it saves time, but for it to 100% solve the issue (despite not being as nice as if C# had support for this type of constraint, built-in) each of the generated methods should still be generic so that

There is no way to do this with a constraint. Another approach though, assuming that PopulateInto can work with a generic N, is to make the core algorihtm generic and private and offer 2 public overloads which take an int and decimal respectively. This will create a similar effect

public static Chart PopulateInto<T>(
  List<T> yAxis, 
  List<decimal> xAxis) {

  return PopulateIntoCore(yAxis, xAxis);
}

public static Chart PopulateInto<T>(
  List<T> yAxis, 
  List<int> xAxis) {

  return PopulateIntoCore(yAxis, xAxis);
}

private static Chart PopulateIntoCore<T, N>(
  List<T> yAxis, 
  List<N> xAxis) where N : struct {
  ...
}

Constraints | Using Generics in C# 2.0, Declaring a BinaryTree<T> Class with No Constraints constraint is the ability to restrict type parameters to a value type or a reference type. I have the following method with generic type: T GetValue<T>(); I would like to limit T to primitive types such as int, string, float but not class type. I know I can define generic for class type like this: C GetObject<C>() where C: class; I am not sure if it is possible for primitive types and how if so.

As Pieter said, you cannot use a compile-time check to to this. However, you can do the following at runtime:

if(!(typeof(N).equals(typeof(int32))) && !(typeof(N).equals(typeof(decimal))))
  // do something

Generic Constraints in C#, In c# generic constraints are used to specify which type of placeholders are allowed with generic class. Following is the example of defining a generic class with type parameter (T) as In case, if we want to restrict a generic class to accept only the particular type where T : struct, The type argument must be a value type. For example, if the generic constraints specifies that only reference type can be used with the generic class then you cannot use value type to create an object of generic type. Constraints can be applied using the where keyword. In the following example, MyGenericClass specifies the constraints that only a reference type can be used with MyGenericClass.

To answer the question in the Title but not the body of the question.

To cover all types commonly meant by Value Types (which includes Nullable Value Types, and also string even though it's technically a Reference type), you need 3 overloads:

public void Foo<T>(T arg) where T : struct
public void Foo<T?>(T? arg) where T : struct
public void Foo<string>(string arg)

From the MSDN Docs on generic constraints:

where T : struct The type argument must be a non-nullable value type.

Generics Constraints - Demystifying C# Generics, They can restrict the parameter that will be replaced with T to some certain type or class or have some properties, like to be new instance of class. If the consumer � How to limit cell entry to numeric value or a list in Excel? Sometimes you design a workbook, and you want to control what people can enter in worksheet. For example, you can limit cell entry to a range of numeric value or a specific list. This article will show you the ways to limit cell value entries in Excel quickly.

Constraining Generics in C#, Here the struct keyword is used to constrain T to a value type. do it for value types, you would use the class keyword to constrain the type to a reference type. We can restrict a generic type to only allow type parameters of a� First, select all the cells you want to restrict. Switch over to the “Data” tab on the Ribbon, and then click the “Data Validation” button. If your window isn’t full size and you can’t see the labels, it’s the icon with two horizontal boxes, a green check mark, and a red crossed circle.

[PDF] Constraints on Type Parameters, When you define a generic class, you can apply restrictions to the kinds of types that client code Constraint. Description where T: struct. The type argument must be a value type. See Using Nullable Types (C# Programming Guide) for more. You can constrain a generic type to a value type by setting the constraint of the type as follows. class ConstrainByValueType<T> where T : struct { } Here the struct keyword is used to constrain T to a value type. The object can then be instantiated like new ConstrainByValueType<double>, and you can

Generic Constraints, Generics allow you to define a class with placeholders for the type of its fields, methods, class MyGenericClass<T> { private T genericMemberVariable; public class then you cannot use value type to create an object of generic type. CHECK Constraint − The CHECK constraint ensures that all the values in a column satisfies certain conditions. INDEX − Used to create and retrieve data from the database very quickly. Constraints can be specified when a table is created with the CREATE TABLE statement or you can use the ALTER TABLE statement to create constraints even after

Comments
  • If those are the only two types you care about I think you could just overload the method. Sure it's 4 overloads but that's not too bad.
  • And my generics are off, that's what I get for writing answers on Friday night, let me correct that.
  • Thank you for your constructive criticism. Unfortunately the question in the title is misleading, because if we limit ourselves to that then the answer is easy: where N : struct. However, the real question only has one real, definitive, answer, and that is "That is not possible with the current allowed C# syntax". I have expanded my answer to cover all the options though, hope it wastes less of peoples time going forward.
  • An alternative way to handle it is to have specific overloads for int or decimal lists.
  • @Mark, yeah, that would be the crux of my answer ;) Fixed
  • Yeah, why not. Throw an InvalidOperationException.