why its not work

Question

float e = 0;  
  
private void button4_Click(object sender, EventArgs e)  
        {  
            if(e >= 0)  
            {  
  
            }  
            j += l / 100;  
            label4.Text = " :mony" + j;  
            //button4.Enabled = true;  
            down();  
        }  

Answer 1

There are two e names — the class member and the parameter of the function — and it is not clear which one should be used.

Try 'if( this.e >= 0 )' or rename the e parameter of button4_Click.

Answer 2

It's better to use more descriptive names for variable, here I don't as I don't know what the meaning of each variable is but this is a basic example.

private float _float1 = 0;
private int _float2 = 0;
private int _float3 = 0;
private void button4_Click(object sender, EventArgs e)
{
    if (_float1 >= 0)
    {

    }

    _float2 += _float3 / 100;
    label4.Text = $@" :mony {_float2}";
    down();
}