Unity: text input box for numerical judgment

Achieve the goal ： Judge the value in the input box

using System;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
public class Calculate : MonoBehaviour
{
    public InputField zhiliangdenshu;// Mass fraction 
    public InputField dianya;// voltage 
    public InputField liuliang;// Traffic 
    public InputField pentou_d;// Nozzle diameter 
    public Text showText;
    double dianyaValue;// Voltage value 
    double liuliangValue;// Flow value 
    double pentou_dValue;// Nozzle diameter 
       public void calculateValue()
    {
        if (IsSpace(zhiliangdenshu.text.ToString())||IsSpace(dianya.text.ToString())||IsSpace(liuliang.text.ToString()) ||IsSpace(liuliang.text.ToString()))// If it is empty 
        {
            showText.text=" An entry is empty ";
            lineShow.SetActive(false);
        }
        else
        {
            dianyaValue = Convert.ToDouble(dianya.text.ToString());//string To double
            switch (zhiliangdenshu.text.ToString())//switch Judge the quality score text character string 
            {
                case "4%":
                    if (( dianyaValue>15&&dianyaValue<19)&& (liuliangValue> 0.5f&&liuliangValue <2.0f) && (pentou_dValue> 0.5f&&pentou_dValue<1.0f))// Judge the value range 
                    {
                        lineShow.transform.localScale = new Vector3(1.5f, 0.5f, 0.5f);
                        // Picture size and form settings 
                    }
                    else
                    {
                        showText.text = " The input value is not within the measurement range ";
                        lineShow.SetActive(false);
                    }; break;
                default:
                    showText.text = " The quality score is entered incorrectly ";
                    lineShow.SetActive(false);
                    break;
            }
        }
    }
    // Detect spaces 
    private bool IsSpace(string textValue)
    {
        if (textValue.Trim().Length == 0)// Remove the spaces at the beginning and end of the string 
        {
            return true;
        }
        return false;
    }