How do I change a sprite in C#?

I’m trying to create a script to randomly change the texture for a group of sprites. I’ve tried

newCell.GetComponent(SpriteRenderer)

but that doesn’t allow access to the sprite, I’ve also tried adding a script to the object whose sprite I’m trying to change using code I’ve found in other answers

var spriteImage : Sprite;

function Start () {

    GetComponent(SpriteRenderer).sprite = spriteImage;

}

But that is javascript and C# can’t seem to find javascript scripts with GetComponent, so I can’t access it that way either. Changing it to C# should look something like this

Sprite spriteImage;
void Start () {
spriteImage = GetComponent(SpriteRenderer).sprite;
}

But it once again can’t access .sprite.

Your GetComponent call does not appear to be syntactically correct.

Try:

Sprite spriteImage;

void Start () {
    spriteImage = GetComponent<SpriteRender>().sprite;
}