What does the 'does not exist in current context' error mean in c sharp?

Answer 1

It means you are trying to modify an entity from outwith the scope of that entity. The following shows an example:

public void button1_Click(object sender, EventArgs e)

{

int x = 42;

timer1.Start();

}

public void timer1_Tick(object sender, EventArgs e)

{

if (x==42) // error: x does not exist in current context

{

// do something...

}

}

Here, the x variable is declared local to the button1_Click event. That is; it is scoped to that function and is only accessible within the context of that function. The timer1_Tick event is a separate function, outwith the scope of the button1_Click event. As such, the timer1_Tick function cannot access x.

In order for both functions to access variable x, that variable must be declared in a scope that is accessible to both functions. Given that both functions are members of the same class, it would make sense to declare x at class scope:

int x = 0;

public void button1_Click(object sender, EventArgs e) {

x = 42;

timer1.Start();

}

public void timer1_Tick(object sender, EventArgs e)

{

if (x==42)

{

// do something...

}

}

Note that the point of declaration defines the scope of the declared entity and that the scope defines the context in which that entity is visible.