Store Type in field/variable
public class Logger
{
    public static Type Writer;

    public static void SetWriter(Type @new)
    {
        Writer = @new;
    }

    public static void Write(string str)
    {
        Writer.Write(str);
    }
}

Writer.Write(str);

public interface IWriter
{
    public Write(string text);
}

public class Logger
{
    public static IWriter Writer;

    public static void SetWriter(IWriter newWriter)
    {
        Writer = newWriter;
    }

    public static void Write(string str)
    {
        Writer.Write(str);
    }
}

public class MyWriter : IWriter
{
    public void Write(string text)
    {
        // Do something to "write" text
    }
}

Logger.SetWriter(new MyWriter());

Type variableName = typeof(SomeTypeName);

Type variableName = someObject.GetType();

public class Logger
{
    public Logger(TextWriter writer)
    {
        _writer = writer;
    }

    private TextWriter _writer;

    public void Write(string text)
    {
        _writer.Write(text);
    }
}