I'm trying to test if a user input is numeric, and if the input is not numeric, a little message box pops up and alerts the user. (I've done this part). The issue I'm having is the and error continues to pop in visual studio

Is this a formatting issue? Should I reformat my code? As you can probably see I am new the C# (and programming).

My code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
namespace wtgCalculator {
public partial class Form1 : Form {
   const double maleratio = 0.536;
   const double femaleratio = 0.492;
    public Form1() {
        InitializeComponent();
    }
    private void textBox1_TextChanged(object sender, EventArgs e) {
    }
    private void Form1_Load(object sender, EventArgs e) {
    }
    private void label1_Click(object sender, EventArgs e) {
    }
    private void textBox1_TextChanged_1(object sender, EventArgs e) {
    }
    private void WaistNumericCheck() {
        double waist;
        string inpwaist = heighttextbox.Text;
        if (double.TryParse(inpwaist, out waist)) {
            MessageBox.Show('Value must be numeric'); //this is where the problem is
        }                                    
    }
 
    private void HeightNumericCheck() {          
        //todo
    }
    private void button1_Click(object sender, EventArgs e) {
        //record inputs to variables
        WaistNumericCheck();
        HeightNumericCheck();
        double height = double.Parse(heighttextbox.Text);
        double waist = double.Parse(waisttextbox.Text);             
        //check is inputs are within boundry          
        CheckDimensions(height, waist);
        //test
       // ShowResult(height, waist);               
    }
    private void CheckLimits(double height, double waist) {
        double result = CalculateRatio(height, waist);
        if (Female.Checked) {
            if (result < femaleratio) {
                MessageBox.Show('Your risk of obesity related cardiovasular is low');
            }
            if (result > femaleratio) {
                MessageBox.Show('Your risk of obesity related to cardiovascular is high');
            }
        }
        if (Male.Checked) {
            if (result < maleratio) {
                MessageBox.Show('Your risk of obesity related cardiovasular is low');
            }
            if (result > maleratio) {
                MessageBox.Show('Your risk of obesity related cardiovasular is High');
            }
        }
        //testing
        MessageBox.Show(result.ToString());
    }
    private void ShowResult(double height, double waist) {
        //double result = CalculateRatio(height, waist);
        //if (Female.Checked) {
        //    if (result < femaleratio) {
        //        MessageBox.Show('Your risk of obesity related cardiovasular is low');
        //    }
        //    if (result > femaleratio) {
        //        MessageBox.Show('Your risk of obesity related to cardiovascular is high');
        //    }
        //}
        //if (Male.Checked) {
        //}
    }
    private static void CheckDimensions(double height, double waist) {
        if (height <= 120) {
            MessageBox.Show('Height must be greater than 120cm');
        }
        if (waist <= 60) {
            MessageBox.Show('Waist must be greater than 60cm');
        }    
    }
    private void Gender_CheckedChanged(object sender, EventArgs e) {
        button1.Enabled = true;                        
    }
    private static double CalculateRatio(double height, double waist) {
       double finalratio = waist / height;
       return finalratio; 
    }
}
}