Unity Error CS1520: Method must have a return type - unity3d

Question

I'm trying to trigger the transition from an idle animation to a running animation when the "d" button is being pressed.
(A link to a tutorial covering a transition like this could also work).
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class IdleToJump : MonoBehaviour
{
bool keyHold = false;
public Form1()
{
InitializeComponent();
}
private void timer1_Tick(object sender, EventArgs e)
{
if (keyHold == true)
{
anim.Play("Run_Anim");
}
}
private void Key_up(object sender, KeyEventArgs e)
{
Key key = (Key)sender;
if (key == "d") {
keyHold = false;
}
}
private void Key_down(object sender, KeyEventArgs e)
{
Key key = (Key)sender;
if (key == "d")
{
keyHold = true;
}
}
}

Answer 1

Cross-check, you're code with this.
Form1 looks like a constructor that somehow got autogenerated. Just comment it out, and add the last two methods inside the class not outside.
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class IdleToJump : MonoBehaviour
{
bool keyHold = false;
//public Form1()//Not sure this constructor is relevant in class, so just comment it
//{
//InitializeComponent();
//}
private void timer1_Tick(object sender, EventArgs e)
{
if (keyHold == true)
{
anim.Play("Run_Anim");
}
private void Key_up(object sender, KeyEventArgs e)
{
Key key = (Key)sender;
if (key == "d") {
keyHold = false;
}
}
private void Key_down(object sender, KeyEventArgs e)
{
Key key = (Key)sender;
if (key == "d")
{
keyHold = true;
}
}
}
}