C#

public async Task<bool> WasItemPurchased(string productId)  
{  
var billing = CrossInAppBilling.Current;  
var result = false;  
try  
{  
var connected = await billing.ConnectAsync(ItemType.InAppPurchase);  
  
if (!connected)  
{  
//Couldn't connect  
return false;  
}  
  
//check purchases  
var verify = new InAppBillingVerify();  
var purchases = await billing.GetPurchasesAsync(ItemType.InAppPurchase, verify);  
  
//check for null just incase  
if (purchases?.Any(p => p.ProductId == productId) ?? false)  
{  
//Purchase restored  
Preferences.Set(productId, true);  
return true;  
}  
else  
{  
//no purchases found  
//Toast.MakeText(this, GetString(Resource.String.Options_RestoreUnavailable), ToastLength.Long);  
return false;  
}  
}  
catch (InAppBillingPurchaseException purchaseEx)  
{  
var message = string.Empty;  
switch (purchaseEx.PurchaseError)  
{  
case PurchaseError.AppStoreUnavailable:  
RestorePurchasesStatusMessage = GetString(Resource.String.Options_PaidFunctions_ErrorAppStoreUnavailable);  
break;  
case PurchaseError.BillingUnavailable:  
RestorePurchasesStatusMessage = GetString(Resource.String.Options_PaidFunctions_ErrorBillingUnavailable);  
break;  
case PurchaseError.PaymentInvalid:  
RestorePurchasesStatusMessage = GetString(Resource.String.Options_PaidFunctions_ErrorPaymentInvalid);  
break;  
case PurchaseError.PaymentNotAllowed:  
RestorePurchasesStatusMessage = GetString(Resource.String.Options_PaidFunctions_ErrorPaymentNotAllowed);  
break;  
case PurchaseError.AlreadyOwned:  
RestorePurchasesStatusMessage = GetString(Resource.String.Options_PaidFunctions_ErrorAlreadyOwned);  
Preferences.Set(productId, true);  
result = true;  
break;  
}  
  
//Decide if it is an error we care about  
if (string.IsNullOrWhiteSpace(message))  
return false;  
  
//Display message to user  
//Toast.MakeText(this, message, ToastLength.Long);  
}  
catch (Exception exception)  
{  
Crashes.TrackError(exception);  
//Something has gone wrong  
RestorePurchasesStatusMessage = GetString(Resource.String.Options_PaidFunctions_ErrorAppStoreUnavailable);  
//Toast.MakeText(this, GetString(Resource.String.Options_PaidFunctions_ErrorAppStoreUnavailable), ToastLength.Long);  
}  
finally  
{  
await billing.DisconnectAsync();  
}  
  
return result;  
}  
  
public async Task<bool> PurchaseItem(string productId, string payload)  
{  
var billing = CrossInAppBilling.Current;  
try  
{  
var connected = await billing.ConnectAsync(ItemType.InAppPurchase);  
if (!connected)  
{  
//we are offline or can't connect, don't try to purchase  
return false;  
}  
  
//check purchases  
var verify = new InAppBillingVerify();  
var purchase = await billing.PurchaseAsync(productId, ItemType.InAppPurchase, payload, verify);  
  
//possibility that a null came through.  
if (purchase == null)  
{  
//did not purchase  
}  
else if (purchase.State == PurchaseState.Purchased)  
{  
//purchased!  
Preferences.Set(productId, true);  
}  
}  
catch (InAppBillingPurchaseException purchaseEx)  
{  
var message = string.Empty;  
switch (purchaseEx.PurchaseError)  
{  
case PurchaseError.AppStoreUnavailable:  
message = GetString(Resource.String.Options_PaidFunctions_ErrorAppStoreUnavailable);  
break;  
case PurchaseError.BillingUnavailable:  
message = GetString(Resource.String.Options_PaidFunctions_ErrorBillingUnavailable);  
break;  
case PurchaseError.PaymentInvalid:  
message = GetString(Resource.String.Options_PaidFunctions_ErrorPaymentInvalid);  
break;  
case PurchaseError.PaymentNotAllowed:  
message = GetString(Resource.String.Options_PaidFunctions_ErrorPaymentNotAllowed);  
break;  
case PurchaseError.AlreadyOwned:  
message = GetString(Resource.String.Options_PaidFunctions_ErrorAlreadyOwned);  
Preferences.Set(productId, true);  
EnableOrDisableProFeatures();  
break;  
}  
  
//Decide if it is an error we care about  
if (string.IsNullOrWhiteSpace(message))  
return false;  
  
//Display message to user  
DisplayToast(message, ToastLength.Long);  
  
}  
catch (Exception exception)  
{  
Crashes.TrackError(exception);  
//Something else has gone wrong, log it  
//Debug("Issue connecting: " + ex);  
DisplayToast(GetString(Resource.String.Options_PaidFunctions_ErrorAppStoreUnavailable), ToastLength.Long);  
  
}  
finally  
{  
await billing.DisconnectAsync();  
}  
return false;  
}  
  
private async Task RestorePurchases()  
{  
var currentConnectivity = Connectivity.NetworkAccess;  
var restorePurchasesResults = new List<bool>();  
if (currentConnectivity == NetworkAccess.Internet)  
{  
restorePurchasesResults.Add(await WasItemPurchased(GetString(Resource.String.Options_PaidFunctions_PurchaseTemplatesAndMoreButtons)));  
restorePurchasesResults.Add(await WasItemPurchased(GetString(Resource.String.Options_PaidFunctions_PurchaseCustomResources)));  
restorePurchasesResults.Add(await WasItemPurchased(GetString(Resource.String.Options_PaidFunctions_PurchaseDisplayWebpageAfterVote)));  
if (restorePurchasesResults.Contains(true))  
{  
DisplayToast(GetString(Resource.String.Options_PaidFunctions_PurchasesRestored), ToastLength.Long);  
  
EnableOrDisableProFeatures();  
}  
else  
{  
if (string.IsNullOrEmpty(RestorePurchasesStatusMessage))  
RestorePurchasesStatusMessage = GetString(Resource.String.Options_PaidFunctions_PurchasesNotFound);  
DisplayToast(RestorePurchasesStatusMessage, ToastLength.Long);  
  
}  
}  
else  
{  
DisplayToast(GetString(Resource.String.Options_InternetUnavailable), ToastLength.Long);  
  
}  
}  
  
private async Task<string> GetProductPrice(string productId)  
{  
var billing = CrossInAppBilling.Current;  
try  
{  
  
var connected = await billing.ConnectAsync(ItemType.InAppPurchase);  
  
if (!connected)  
{  
//Couldn't connect  
return string.Empty;  
}  
  
//check purchases  
var item = await billing.GetProductInfoAsync(ItemType.InAppPurchase, productId);  
  
if (item != null)  
return item.ToList()[0].LocalizedPrice;  
}  
catch (InAppBillingPurchaseException purchaseEx)  
{  
var message = string.Empty;  
switch (purchaseEx.PurchaseError)  
{  
case PurchaseError.AppStoreUnavailable:  
message = GetString(Resource.String.Options_PaidFunctions_ErrorAppStoreUnavailable);  
break;  
case PurchaseError.BillingUnavailable:  
message = GetString(Resource.String.Options_PaidFunctions_ErrorBillingUnavailable);  
break;  
case PurchaseError.PaymentInvalid:  
message = GetString(Resource.String.Options_PaidFunctions_ErrorPaymentInvalid);  
break;  
case PurchaseError.PaymentNotAllowed:  
message = GetString(Resource.String.Options_PaidFunctions_ErrorPaymentNotAllowed);  
break;  
}  
  
//Decide if it is an error we care about  
if (string.IsNullOrWhiteSpace(message))  
return string.Empty;  
  
//Display message to user  
DisplayToast(message, ToastLength.Long);  
  
}  
catch (Exception exception)  
{  
Crashes.TrackError(exception);  
//Something has gone wrong  
}  
finally  
{  
await billing.DisconnectAsync();  
}  
return string.Empty;  
}

while (reader.Read())
{ 
txtPrice.Text = Convert.ToDouble(reader["Price"]).ToString("C",info);
}
<pre>

But if I remove the currency format and use custom format for the textbox "Unit Price" everything work fine but I really want the currency format on the unit Price txtBox. 
See when the format is removed and the custom format is used see code below and  image 2. 

<pre>
while (reader.Read())
{ 
txtPrice.Text = Convert.ToDouble(reader["Price"]).ToString("#,00.00");




SUBTOTAL CALCULATION CODE

private void Subtolcalculation()
        {

            for (int i = 0; i < dataGVfrontsale.Rows.Count - 1; i++)

            {
                CultureInfo info;
                info = new CultureInfo("en-NG");

                double colPrice = double.Parse(dataGVfrontsale.Rows[i].Cells[4].Value.ToString());
                double colQty = double.Parse(dataGVfrontsale.Rows[i].Cells[5].Value.ToString());
                double subtol = colPrice * colQty;

                dataGVfrontsale.Rows[i].Cells[7].Value = subtol;//.ToString("C", info);

               
            }

CODE FOR TOTAL QUANTITY / CURRENCY


private double Total1()

        {
            double totl = 0;

            int i = 0;
            for (i = 0; i < dataGVfrontsale.Rows.Count; i++)
            {
                totl = totl + Convert.ToDouble(dataGVfrontsale.Rows[i].Cells[5].Value);
            }

            return totl;

        }

public void calculColumns()
        {
            //Currency Symbol  total on Textbox 
            CultureInfo info;
            info = new CultureInfo("en-NG");
           

            txtTolQty.Text = Total1().ToString("C", info);



            //txtGrndTl.Text = Total22().ToString("#,00.00");

            //txtFinalTot.Text = Total22().ToString("C", info);

            
         }
<pre>

using System;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.IO;
using System.Text;
using System.Windows.Forms;
using MessageBox = System.Windows.Forms.MessageBox;
using System.Threading;

class Folders
{
#pragma warning disable IDE1006 // Naming Styles
    public string pth { get; set; }
}

namespace Backup_Tool
{

    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            foreach (var Drives in Environment.GetLogicalDrives())
            {
                System.IO.DriveInfo DriveInf = new System.IO.DriveInfo(Drives);
                if (DriveInf.IsReady == true)
                {
                    ddlDrives.Items.Add(DriveInf.Name);
                }
            }
            ListView1.Items.Add(new Folders() { pth = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory) });
            ListView1.Items.Add(new Folders() { pth = Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments) });
            ListView1.Items.Add(new Folders() { pth = Environment.GetFolderPath(Environment.SpecialFolder.UserProfile) + "\\" + "Downloads" });
            ListView1.Items.Add(new Folders() { pth = Environment.GetFolderPath(Environment.SpecialFolder.MyMusic) });
            ListView1.Items.Add(new Folders() { pth = Environment.GetFolderPath(Environment.SpecialFolder.MyPictures) });
            ListView1.Items.Add(new Folders() { pth = Environment.GetFolderPath(Environment.SpecialFolder.MyVideos) });
        }

        public void ChkDest()
        {
            string message = "You must first select a destination";
            string title = "Destination Error";
            MessageBoxButtons buttons = MessageBoxButtons.OK;
            MessageBox.Show(message, title, buttons, MessageBoxIcon.Warning);
        }

        private void Cls_Click(object sender, RoutedEventArgs e)
        {
            System.Windows.Application.Current.Shutdown();
        }

        private void AddFolder_Click(object sender, RoutedEventArgs e)
        {
            var fbd = new FolderBrowserDialog { };
            if (fbd.ShowDialog().ToString().Equals("OK"))
                ListView1.Items.Add(new Folders() { pth = fbd.SelectedPath });
        }

        private void FullSystem_Click(object sender, RoutedEventArgs e)
        {
            ChkDest();
        }

        private void DelFolder_Click(object sender, RoutedEventArgs e)
        {
            ListView1.Items.RemoveAt(ListView1.SelectedIndex);
        }

        private void FldBackup_Click(object sender, RoutedEventArgs e)
        {
            if (ddlDrives.SelectedIndex > -1 && ddlDrives.SelectedItem != null && !string.IsNullOrEmpty(ddlDrives.SelectedItem.ToString()))
            {
                foreach (Folders item in ListView1.Items.Cast<folders>())
                {
                    DirectoryInfo source = new DirectoryInfo(item.pth);
                    string fldname = new DirectoryInfo(item.pth).Name;
                    DirectoryInfo target = new DirectoryInfo(ddlDrives.SelectedItem + "DataHistory\\" + fldname + "\\");

                    var bkpthread = new Thread(CopyDirectory(source.ToString(), target.ToString()))
                    {
                        IsBackground = true
                    };
                    bkpthread.Start();

                    //CopyDirectory(source.ToString(),target.ToString());
                }
            }
            else
            {
                ChkDest();
            }
        }

        private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            if (ddlDrives.SelectedItem.ToString().Contains("C"))
            {
                FlashTB.Visibility = Visibility.Visible;
                tblk1.Visibility = Visibility.Visible;
            }
            else
            {
                FlashTB.Visibility = Visibility.Hidden;
                tblk1.Visibility = Visibility.Hidden;
            }
        }
        public void CopyDirectory(string SourceDirectory, string TargetDirectory)
        {
            string ErrorLog = "c:\\temp\\log.txt";
            DirectoryInfo source = new DirectoryInfo(SourceDirectory);
            DirectoryInfo target = new DirectoryInfo(TargetDirectory);

            //Determine whether the source directory exists.
            try
            {
                if (!source.Exists)
                    return;
                if (!target.Exists)
                    Directory.CreateDirectory(target.FullName);
            }
            catch (IOException errorCreate)
            {
                using (StreamWriter writer = new StreamWriter(ErrorLog))
                {
                    writer.WriteLine(errorCreate.Message);
                }
            }

            //Copy files.
            try
            {
                FileInfo[] sourceFiles = source.GetFiles();
                for (int i = 0; i < sourceFiles.Length; ++i)
                    File.Copy(sourceFiles[i].FullName, target.FullName + "\\" + sourceFiles[i].Name, true);
            }
            catch (IOException copyError)
            {
                using (StreamWriter writer = new StreamWriter(ErrorLog))
                {
                    writer.WriteLine(copyError.Message);
                }
            }

            //Copy directories.
            try
            {
                DirectoryInfo[] sourceDirectories = source.GetDirectories();
                for (int j = 0; j < sourceDirectories.Length; ++j)
                    CopyDirectory(sourceDirectories[j].FullName, target.FullName + "\\" + sourceDirectories[j].Name);
            }
            catch (IOException errorDir)
            {
                using (StreamWriter writer = new StreamWriter(ErrorLog))
                {
                    writer.WriteLine(errorDir.Message);
                }
            }
        }
    }
}

private string GetVendorInitials(string tableName, int jobId)
{
    using (var db = GetDataContext())
    {
        var result = string.Empty;

        var vendorNames = (from jhv in db.GetTable()  //<========== THIS IS WHAT I CAN'T FIGURE OUT
                            join c in db.Companies on jhv.VendorId equals c.Id
                            where jhv.JobId == jobId
                            select c.CompanyName).ToList();

        foreach (var vendorName in vendorNames)
        {
            var vendorInits = new string(vendorName.Split(' ').Select(x => x[0]).ToArray());
            result = result + vendorInits + ",";
        }
        result = result.Trim();
        result = result.Substring(0, result.Length - 1);

        return result;
    }
}