XNA 4.0 CameraPosition Question

Here is my code for moving the camera:

    float camTurn = 0.0f;
    float camForwardBack = 0.0f;

    // Set the position of the model in world space, and set the rotation.
    Vector3 modelPosition = new Vector3(-200.0f, -175.0f, 10050.0f);
    float modelRotation = 0.0f;

    // Set the position of the camera in开发者_开发问答 world space, for our view matrix.
    Vector3 cameraPosition = new Vector3(camTurn, 0.0f, camForwardBack);


    public void Movement()
    {
        if (Keyboard.GetState().IsKeyDown(Keys.W))
            camForwardBack = camForwardBack + 1;
        else if (Keyboard.GetState().IsKeyDown(Keys.S))
            camForwardBack = camForwardBack - 1;
        else if (Keyboard.GetState().IsKeyDown(Keys.A))
            camTurn = camTurn - 1;
        else if (Keyboard.GetState().IsKeyDown(Keys.D))
            camForwardBack = camForwardBack + 1;

    }

The thing is camTurn and CamForwardBack have red squigglies under them and give the error:

A field intializer cannot reference the non-static field, method, or property.

Try to initialise the variables in the constructor first.

Like:

public class MyCam
{
  float camTurn = 0.0f;
  float camForwardBack = 0.0f;

  // Set the position of the model in world space, and set the rotation.
  Vector3 modelPosition = new Vector3(-200.0f, -175.0f, 10050.0f);
  float modelRotation = 0.0f;

  // Set the position of the camera in world space, for our view matrix.
  Vector3 cameraPosition = new Vector3(camTurn, 0.0f, camForwardBack);

  public MyCam()
  {
     camTurn = 0;
     camForwardBack = 0;
  }

  public void Movement()
  {
    if (Keyboard.GetState().IsKeyDown(Keys.W))
        camForwardBack = camForwardBack + 1;
    else if (Keyboard.GetState().IsKeyDown(Keys.S))
        camForwardBack = camForwardBack - 1;
    else if (Keyboard.GetState().IsKeyDown(Keys.A))
        camTurn = camTurn - 1;
    else if (Keyboard.GetState().IsKeyDown(Keys.D))
        camForwardBack = camForwardBack + 1;

  }