How to access and create if statement variables C#

I'm trying to keep to the DRY principle in C#, and I was wondering if it's possible to access the argument checks in an if block. For example, would the below be possible?

if (foo == true || bar == false)
{
  if (check0)
  {
    //foo is true
  }
  if (!check1)
  {
    //bar is false
  }
}

I was also wondering if it's possible to do this, to keep the scope clean?:

if (var foo = runTimeAccessedVariable == "bar")
{
  //we now have the runtime generated variable.
}
//but it doesn't exist here