GetMethod returning null c#

I don't understand why GetMethod return null - two times at method1 and method

Type model = AssemblyHelper.GetTypeByClassName(Assembly.GetExecutingAssembly(), modelName + MappingColums.Tokens.Validation); // MappingColums.Tokens.Validation = "Validation"

for testing purpose I try get method twice:

MethodInfo method1 = model.GetType().GetMethod(MappingColums.Tokens.Get + modelName); // MappingColums.Tokens.Get + modelName = "Get" + "Product"
MethodInfo method = model.GetType().GetMethods().FirstOrDefault(x => x.Name == MappingColums.Tokens.Get + modelName && x.GetParameters().Count() == 0);
object result = method.Invoke(model, null);

below class and method that I want to use by reflection.

public class ProductValidation
{
    private IProductRepository repositoryProduct;

    public ProductValidation(IProductRepository repoProduct)
    {
        repositoryProduct = repoProduct;
    }

    public ICollection<Product> GetProduct()
    {
        return repositoryProduct.Products.ToList();
    }

}

I do not know if it matters, but I'm using ASP.NET Core MVC. Where I debug Type model just behind AssemblyHelper.GetTypeByClassName there is at Declared Methods: {System.Collections.Generic.ICollection1[AureliaCMS.Models.Entities.Product] GetProduct()}

Please give me advice where to look up for issue.