Why is subscribed event always null?

Why is subscribed event always null?

I declare a subscription to event in "MainClass.cs":
{
public void btndel_bar_Click(object sender, RoutedEventArgs e)
{
SomeClass sc = new SomeClass();
sc.FieldUpdate += new SomeClass.FieldUpdateHandler(sc_FieldUpdate);
}
void sc_FieldUpdate(object sender, ValueEventArgs e)
{
MessageBox.Show(e.Smth_property);
}
}
And here is I want to listen event:
"Someclass.cs":
{
public delegate void FieldUpdateHandler(object sender, ValueEventArgs e);
public event FieldUpdateHandler FieldUpdate;
ValueEventArgs a1 = new ValueEventArgs(ID_Empl.ToString());
FieldUpdate(this, a1);
public SomeClass()
{
Somemethod();
}
void Somemethod()
{
string str = "Steel";
ValueEventArgs args = new ValueEventArgs(str);
FieldUpdate(this, args);
}
A class which carries data:
public class ValueEventArgs : EventArgs
{
private string smth;
public ValueEventArgs(string smth)
{
this.smth = smth;
}
public string Someth_property
{
get { return smth; }
}
}
I always have FieldUpdate=null. How to solve it?