错误消息：并非所有代码路径都返回一个值

Question

I get this error message in the following line of my code:

public async Task<bool> TestMakePurchase(string productId, string payload)

Error CS0161: 'Game1.TestMakePurchase(string, string)': not all code paths return a value (CS0161)

What does this error message mean and what is wrong with my code?

Full code:

 async void CheckPurchase()
    {

        bool purchaseIsSuccessful = await TestMakePurchase("com.website.appName.purchaseName", "");          

        if (purchaseIsSuccessful)
        {               

        }
        else
        {

        }
    }


    public async Task<bool> TestMakePurchase(string productId, string payload)
    {
        var billing = CrossInAppBilling.Current;
        try
        {
            var connected = await billing.ConnectAsync();
            if (!connected)
            {                 
                return false;
            }


            var purchase = await billing.PurchaseAsync(productId, ItemType.InAppPurchase, payload);

            if (purchase == null)
            {
                return false;
            }
            else
            {
                return true;
            }
        }
        catch (InAppBillingPurchaseException purchaseEx)
        {

        }

        finally
        {
            await billing.DisconnectAsync();
        }
    }

Answer 1

If the first try catches an exception, it potentially bypasses all of you return statements. You can fix this by adding a return right at the end of your method:

public async Task<bool> TestMakePurchase(string productId, string payload)
{
    var billing = CrossInAppBilling.Current;
    try
    {
        // Snip
    }
    catch (InAppBillingPurchaseException purchaseEx)
    {

    }
    finally
    {
        await billing.DisconnectAsync();
    }

    // Add this line
    return false;
}

Answer 2

If exception occur in try block the code exit without any return value. Please add return statements after finally block.

Answer 3

You don't have to call return on each conditional statement. Simply track the state with a variable ( purchaseState ). It is unclear what should happen when a InAppBillingPurchaseException is thrown. I would at least log this error.

public async Task<bool> TestMakePurchase(string productId, string payload)
{   
    var purchaseSuccesful = false;
    var billing = CrossInAppBilling.Current;
    try
    {                                   
        if (await billing.ConnectAsync())
        {                 
            var purchase = await billing.PurchaseAsync(productId, ItemType.InAppPurchase, payload);
            purchaseSuccesful = purchase != null;
        }
    }
    catch (InAppBillingPurchaseException purchaseEx)
    {
        //log this error?
    }
    finally
    {
        await billing.DisconnectAsync();
    }

    return purchaseSuccesful;
}