Question

有一个类似的问题here，但我认为这涉及不同的原因。

我将一个班级从一个较新的项目转移到一个较旧的项目中。两者都针对.net 4.6但是在移动之后我在构建时收到了以下错误。

功能＆＃39;插值字符串＆＃39;在C＃5中不可用。请使用语言版本6或更高版本。

我尝试将项目设置为在属性窗口中使用C＃6进行构建而不做任何更改。

Answer 1

我最终找到了改变它的地方。有时，当您更新目标框架版本时，这不会发生变化。

Answer 2

安装DotNetCompilerPlatform版本2.1.0

Answer 3

将此添加到您的web.config。安装DotNetCompilerPlatform后，它可能会自动添加。

<system.codedom>
  <compilers>
    <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.CSharpCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:default /nowarn:1659;1699;1701" />
    <compiler language="vb;vbs;visualbasic;vbscript" extension=".vb" type="Microsoft.CodeDom.Providers.DotNetCompilerPlatform.VBCodeProvider, Microsoft.CodeDom.Providers.DotNetCompilerPlatform, Version=2.0.1.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" warningLevel="4" compilerOptions="/langversion:default /nowarn:41008 /define:_MYTYPE=\&quot;Web\&quot; /optionInfer+" />
  </compilers>
</system.codedom>

Answer 4

（它可以轻松适用于VS 2019-.NET Framework 4.8 Web应用程序项目）

在安装DotNetCompilerPlatform v3.6之后我已经意识到了这个问题

我一直在寻找TheColonel26的答案，但无法更改所选的语言版本：

显然，我们不能更改所选语言的版本。（For details look here）

此后，我使用了kfwbird的答案，但对较新版本进行了更改：

using System;
using Xamarin.Forms.Platform.iOS;
using Foundation;
using UIKit;
using Xamarin.Forms;
using CoreGraphics;
using EficienciaEnergetica.iOS.KeyboardOverlap;
using System.Diagnostics;
using EficienciaEnergetica.ContentPages;

[assembly: ExportRenderer(typeof(Page), typeof(KeyboardOverlapRenderer))]
namespace EficienciaEnergetica.iOS.KeyboardOverlap
{
    [Preserve(AllMembers = true)]
    public class KeyboardOverlapRenderer : PageRenderer
    {

        Rectangle initialViewState;


        NSObject _keyboardShowObserver;
        NSObject _keyboardHideObserver;
        private bool _pageWasShiftedUp;
        private double _activeViewBottom;
        private bool _isKeyboardShown;

        public static void StaticInit()
        {
            var now = DateTime.Now;
            Debug.WriteLine("Keyboard Overlap plugin initialized {0}", now);
        }

        public override void ViewWillAppear(bool animated)
        {
            base.ViewWillAppear(animated);

            var page = Element as ContentPage;

            if (page != null)
            {
                var contentScrollView = page.Content as ScrollView;

                if (contentScrollView != null)
                    return;

                initialViewState = Element.Bounds;

                RegisterForKeyboardNotifications();
            }
        }

        public override void ViewWillDisappear(bool animated)
        {
            base.ViewWillDisappear(animated);

            UnregisterForKeyboardNotifications();
        }

        void RegisterForKeyboardNotifications()
        {
            if (_keyboardShowObserver == null)
                _keyboardShowObserver = NSNotificationCenter.DefaultCenter.AddObserver(UIKeyboard.WillShowNotification, OnKeyboardShow);
            if (_keyboardHideObserver == null)
                _keyboardHideObserver = NSNotificationCenter.DefaultCenter.AddObserver(UIKeyboard.WillHideNotification, OnKeyboardHide);
        }

        void UnregisterForKeyboardNotifications()
        {
            _isKeyboardShown = false;
            if (_keyboardShowObserver != null)
            {
                NSNotificationCenter.DefaultCenter.RemoveObserver(_keyboardShowObserver);
                _keyboardShowObserver.Dispose();
                _keyboardShowObserver = null;
            }

            if (_keyboardHideObserver != null)
            {
                NSNotificationCenter.DefaultCenter.RemoveObserver(_keyboardHideObserver);
                _keyboardHideObserver.Dispose();
                _keyboardHideObserver = null;
            }
        }

        protected virtual void OnKeyboardShow(NSNotification notification)
        {
            if (!IsViewLoaded)
                return;

            _isKeyboardShown = true;
            var activeView = View.FindFirstResponder();

            if (activeView == null)
                return;

            var keyboardFrame = UIKeyboard.FrameEndFromNotification(notification);
            var isOverlapping = activeView.IsKeyboardOverlapping(View, keyboardFrame);

            if (!isOverlapping)
                return;

            if (isOverlapping)
            {
                System.Diagnostics.Debug.WriteLine(keyboardFrame);
                _activeViewBottom = activeView.GetViewRelativeBottom(View);
                ShiftPageUp(keyboardFrame.Height, _activeViewBottom);
            }
        }

        private void OnKeyboardHide(NSNotification notification)
        {
            if (!IsViewLoaded)
                return;

            _isKeyboardShown = false;
            var keyboardFrame = UIKeyboard.FrameEndFromNotification(notification);

            if (_pageWasShiftedUp)
                ShiftPageDown(keyboardFrame.Height, _activeViewBottom);
        }

        private void ShiftPageUp(nfloat keyboardHeight, double activeViewBottom)
        {
            var pageFrame = initialViewState;// Element.Bounds;

            var newY = pageFrame.Y + CalculateShiftByAmount(pageFrame.Height, keyboardHeight, activeViewBottom);

            Element.LayoutTo(new Rectangle(pageFrame.X, newY,
                pageFrame.Width, pageFrame.Height));

            _pageWasShiftedUp = true;
        }

        private void ShiftPageDown(nfloat keyboardHeight, double activeViewBottom)
        {
            Element.LayoutTo(initialViewState);
            _pageWasShiftedUp = false;
        }

        private double CalculateShiftByAmount(double pageHeight, nfloat keyboardHeight, double activeViewBottom)
        {
            return (pageHeight - activeViewBottom) - keyboardHeight;
        }
    }
}

现在它可以正常工作了。

功能＆＃39;插值字符串＆＃39;在C＃5中不可用。请使用语言版本6或更高版本

4 个答案: