You can write
" "
instead of
new String(' ')
Does that help?
Depending on what you do, you might want to look into the StringBuilder.Append overload that accepts a character and a 'repeat' count:
var tabs = new StringBuilder();
tabs.Append(' ', 8);
or into the string constructor that constructs a string from a character a 'repeat' count:
var tabs = new string(' ', 8);
Here's an enterprisey OO solution to satisfy all your space generation needs:
public abstract class SpaceFactory
{
    public static readonly SpaceFactory Space = new SpaceFactoryImpl();
    public static readonly SpaceFactory ZeroWidth = new ZeroWidthFactoryImpl();
    protected SpaceFactory { }
    public abstract char GetSpace();
    public virtual string GetSpaces(int count)
    {
        return new string(this.GetSpace(), count);
    }
    private class SpaceFactoryImpl : SpaceFactory
    {
        public override char GetSpace()
        {
            return '\u0020';
        }
    }
    private class ZeroWidthFactoryImpl : SpaceFactory
    {
        public override char GetSpace()
        {
            return '\u200B';
        }
    }
}