我正在尝试使用插件 InAppBilling为 Xamarin 表单解决方案实现（应用程序内计费）我找不到这个插件的任何完整代码示例或文档，除了这个我一步一步按照说明进行操作，但是当我运行我的代码时，我得到这个例外

{System.NullReferenceException: Current Context/Activity is null，确保 MainApplication.cs 文件在您的源代码中设置 CurrentActivity，以便 In App Billing 可以使用它。在 Plugin.InAppBilling.InAppBillingImplementation.get_Context () [0x00000] 在 C:\projects\inappbillingplugin\src\Plugin.InAppBilling.Android\InAppBillingImplementation.cs:59 在 Plugin.InAppBilling.InAppBillingImplements. itemType) [0x00000] in C:\projects\inappbillingplugin\src\Plugin.InAppBilling.Android\InAppBillingImplementation.cs:372 at myproject.MainPage+d__28.MoveNext () [0x00051] in C:\Users\xuser\source\repos \myproject\MainPage.xaml.cs:415 }

我的示例代码
此代码位于（共享/可移植类库/.NET 标准）

主页.xaml.cs

 public partial class MainPage : ContentPage
    {

     void OnPurchased(object sender, EventArgs e)
            {
              InAppBilling();
            }
     async void InAppBilling()
            {
                try
                {
                    var productId = "xxxxx.xxxx_appbilling";
                    var connected = await CrossInAppBilling.Current.ConnectAsync();
                    if (!connected)
                    {
                        //Couldn't connect …

我有tablix名为tablix2并且有3列,我想计算Tablix范围内2个文本框中的行总数和计数,我试试这个表达式.

=RowNumber("Tablix2")

和

=CountRows("Tablix2")

和

=Count(Fields!ID.Value,"Tablix2")

它始终显示此错误消息:

文本框'Textbox7'的Value表达式具有对聚合函数无效的作用域参数.scope参数必须设置为字符串常量,该常量等于包含组的名称,包含数据区域的名称或数据集的名称.

C# 代码

public List<searchProducts_Result> GetProducts()
{
            var nameParam = new ObjectParameter("numbers", typeof(int));
            List<searchProducts_Result> listobjs = new List<searchProducts_Result>();
            ObjectResult<searchProducts_Result> objResult = null;
            searchProducts_Result outParam = new searchProducts_Result();
            using (var db = new SPWebEntities())
            {
                objResult = db.searchProducts("asd", 2, 5, "15", nameParam);
                if (nameParam.Value != null)
                    outParam.UserID = nameParam.Value.ToString();
                else
                    outParam.UserID = "0";
               listobjs.Add(outParam);
                foreach (searchProducts_Result sr in objResult)
                {
                    listobjs.Add(sr);
                }
            }

            return listobjs;
}

我的存储过程：

[searchProducts]
    @productName varchar(50),
    @pageStart int=2,
    @pageEnd int=4,
    @result varchar(MAX),
    @numbers int output
as
   select @numbers …

我不想通过自定义渲染器的社交媒体分享链接

public class CustomActions : ICustomActions
    {
        Context context = Android.App.Application.Context;

        public void ShareThisLink()
        {
            Intent sharingInt = new Intent(Android.Content.Intent.ActionSend);
            sharingInt.SetType("text/plain");
            string shareBody = "https://www.google.com";
            sharingInt.PutExtra(Android.Content.Intent.ExtraSubject, "Subject");
            sharingInt.PutExtra(Android.Content.Intent.ExtraText, shareBody);
            context.StartActivity(Intent.CreateChooser(sharingInt, "Share via"));
        }

    }

发生此错误

Android.Util.AndroidRuntimeException: Calling startActivity() from outside of an Activity  context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?

即使我添加下面的代码我仍然得到相同的错误

 sharingInt.AddFlags(ActivityFlags.NewTask);