How can I load a user control[s] in a window dynamically (using code at runtime)?
For adding multiple controls you need container.
Suppose you have a StackPanel container "myStack"
You can create control dynamically and add it to container. See code below
void AddButtons()
{
Button B1=new Button(),B2=new Button(), B3=new Button();
B1.Content="Hello";
B2.Content="First";
B3.content="Application";
// Now you can set more properties like height, width, margin etc...
MyStack.Children.Add(B1);
MyStack.Children.Add(B2);
MyStack.Children.Add(B2);
}