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Nullable scalar types and LiveBindings


Nullable scalar types and LiveBindings

By : user2949412
Date : November 17 2020, 01:00 AM
With these it helps Here is how you register the type conversion for Nullable to string and vice versa in the LiveBindings engine:
code :
procedure RegisterNullableConversions;
begin
  TValueRefConverterFactory.UnRegisterConversion(TypeInfo(Nullable<string>), TypeInfo(string));
  TValueRefConverterFactory.RegisterConversion(TypeInfo(Nullable<string>), TypeInfo(string),
    TConverterDescription.Create(
      procedure(const I: TValue; var O: TValue)
      begin
        if I.AsType<Nullable<string>>.HasValue then
          O := I.AsType<Nullable<string>>.Value
        else
          O := 'null';
      end,
      'NullableToString', 'NullableToString', EmptyStr, True, EmptyStr, nil)
  );
  TValueRefConverterFactory.UnRegisterConversion(TypeInfo(string), TypeInfo(Nullable<string>));
  TValueRefConverterFactory.RegisterConversion(TypeInfo(string), TypeInfo(Nullable<string>),
    TConverterDescription.Create(
      procedure(const I: TValue; var O: TValue)
      begin
        O := TValue.From<Nullable<string>>(I.AsString);
      end,
      'StringToNullable', 'StringToNullable', EmptyStr, True, EmptyStr, nil)
  );
end;


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Class in c# (with filehelpers) - nullable strings giving an error when other nullable types aren't

Class in c# (with filehelpers) - nullable strings giving an error when other nullable types aren't


By : user3192044
Date : March 29 2020, 07:55 AM
around this issue string is reference type, reference types are nullable in their nature.
When you define public string ItemNum, it is already nullable.
code :
public struct Nullable<T> where T : struct, new()
Getting type definition for nullable types breaks code for non-nullable types

Getting type definition for nullable types breaks code for non-nullable types


By : mamilldo
Date : March 29 2020, 07:55 AM
hop of those help? Here is the MSDN documentation on checking for nullable types
It looks like you need to add the following:
code :
if(t.IsGenericType && ...
Nullable "scalar navigation properties" in EF 4.0: Mapping a non-nullable column from a separate database tabl

Nullable "scalar navigation properties" in EF 4.0: Mapping a non-nullable column from a separate database tabl


By : user7752180
Date : March 29 2020, 07:55 AM
it should still fix some issue There is a rather "dirty" solution that should work. It would require some code changing but would leave your Foo entity with field A and B.
Foo class:
code :
class Foo {
   [Key]
   public int FooId { get; set; }
   public int A { get; set; }
   [NotMapped]
   public int? B {
      get {
         return FooB == null ? null : FooB.B;
      }
      set {
         if(value == null) {
            FooB = null;
         } else {
            if(FooB == null)
               FooB = new FooB();
            FooB.B = (int)value;
         }
   public virtual FooB FooB{ get; set; }
}
 class FooB {
    [Key, ForeignKey("FooId")]
    public int FooId { get; set; }
    public int B { get; set; }
 }
Typelite: how to set nullable C# types to nullable Typescript types with T4 transform?

Typelite: how to set nullable C# types to nullable Typescript types with T4 transform?


By : Wang Ji
Date : March 29 2020, 07:55 AM
hope this fix your issue I'm using Typelite 9.5.0 to convert my C# classes to Typescript interfaces. I want that a nullable type in (e.g. Guid?) is converted to a nullable type in Typescript. , If you want to use a TypeLite formatter this should work:
code :
var propertyInfo = tsprop.ClrProperty as PropertyInfo;
var propertyType = propertyInfo != null ? propertyInfo.PropertyType : ((FieldInfo)tsprop.ClrProperty).FieldType;    
var isNullabe = Nullable.GetUnderlyingType(propertyType) != null;
if (isNullabe) {
    return identifier.Name + "? ";
}
Nullable reference types unexpected CS8629 Nullable value type may be null with temporary variables

Nullable reference types unexpected CS8629 Nullable value type may be null with temporary variables


By : NinaCAS
Date : March 29 2020, 07:55 AM
Any of those help This is just a temporary answer until Julien Couvreur, one of the designers of nullable reference types posts the definitive answer (nagging). I'm posting this here because the question will be asked again once C# 8 is released.
As Julien answers in 3 Github issues #34800 , #37032 and #36149 this is a known limitation of the C# 8 analyzer that's out of scope for C# 8.
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