Class Mapping Error: 'T' must be a non-abstract type with a public parameterless constructor

Question

While mapping class i am getting error \'T\' must be a non-abstract type with a public parameterless constructor in order to use it as parameter \'T\' in the generic type or

Answer 1

The problem is that you're trying to use the T from SqlReaderBase as the type argument for MapperBase - but you don't have any constraints on that T.

Try changing your SqlReaderBase declaration to this:

public abstract class SqlReaderBase : ConnectionProvider
    where T : new()

Here's a shorter example which demonstrates the same issue:

class Foo
{
    Bar bar;
}

class Bar where T : new()
{
}

The fix is to change Foo's declaration to:

class Foo where T : new()

Then the compiler will know that the T from Foo is a valid type argument for Bar.