Trying to create a type in Roslyn from a Type, but I get BadImageFormatException when converting a nullable

Question

I'm trying to write a function that takes in an existing Type, and converts the Type to a PropertyDeclaration. I almost have it working, but if the Type I pass in is Nullable, I get this error when I eventually try to compile my class with it: System.BadImageFormatException: is not a valid Win32 application. (Exception from HRESULT: 0x800700C1).

Here's my code:

var classDeclaration = SyntaxFactory.ClassDeclaration("class name");
classDeclaration.AddModifiers(SyntaxFactory.Token(SyntaxKind.PublicKeyword));
classDeclaration.AddMembers(ConvertToProperty(myType, myTypeName));

private static PropertyDeclarationSyntax ConvertToProperty(Type propertyType, string propertyName)
{
    var typeSyntax = SyntaxFactory.ParseTypeName(propertyType.ToString());
    var propertyDeclaration = SyntaxFactory.PropertyDeclaration(typeSyntax, propertyName)
        .AddModifiers(SyntaxFactory.Token(SyntaxKind.PublicKeyword))
        .AddAccessorListAccessors(
            SyntaxFactory.AccessorDeclaration(SyntaxKind.GetAccessorDeclaration).WithSemicolonToken(SyntaxFactory.Token(SyntaxKind.SemicolonToken)),
            SyntaxFactory.AccessorDeclaration(SyntaxKind.SetAccessorDeclaration).WithSemicolonToken(SyntaxFactory.Token(SyntaxKind.SemicolonToken)));

    return propertyDeclaration;
}

The class will compile just fine if the Type I pass in is not nullable. I'm not very familiar with Roslyn and I haven't found any examples online of someone doing what i'm trying to do. Is anyone more familiar and has an idea?

Answer 1

First, you really need to add more details to your question. Look here: Minimal, Complete, and Verifiable example

To your problem, when you run your code on a non nullable type, lets say int you will get this output:

public class MyClass
{
    public System.Int32 MyProperty { get; set; }
}

But with nullable , you will get this:

public class MyClass
{
    public System.Nullable`1[System.Int32] MyProperty { get; set; }
}

You can see that it is not a valid C# code.

To solve it, check this answer , just copy paste and the result will look like this:

public class MyClass
{
    public Nullable<Int32> MyProperty { get; set; }
}

Full code:

private static PropertyDeclarationSyntax ConvertToProperty(Type propertyType, string propertyName)
{
    var typeSyntax = ParseTypeName(propertyType.ToGenericTypeString());
    return PropertyDeclaration(typeSyntax, propertyName)
            .AddModifiers(Token(SyntaxKind.PublicKeyword))
            .AddAccessorListAccessors(
                AccessorDeclaration(SyntaxKind.GetAccessorDeclaration).WithSemicolonToken(Token(SyntaxKind.SemicolonToken)),
                AccessorDeclaration(SyntaxKind.SetAccessorDeclaration).WithSemicolonToken(Token(SyntaxKind.SemicolonToken)));
}

var classDeclaration = ClassDeclaration("MyClass");
classDeclaration = classDeclaration.AddModifiers(Token(SyntaxKind.PublicKeyword));
classDeclaration = classDeclaration.AddMembers(ConvertToProperty(typeof(int?), "MyProperty"));

Console.WriteLine(classDeclaration.ToString());