在 Xamarin 表单的命名空间中找不到类型答案

【问题标题】：Type not found in NameSpace in Xamarin Forms在 Xamarin 表单的命名空间中找不到类型
【发布时间】：2017-04-10 06:30:32
【问题描述】：

我是 Xamarin 的新手，在使用 Xamarin 表单时遇到问题。我在我的命名空间中添加了名为 NamedColor.cs 的新文件，并在我的 ListViewDemoPage.xaml 文件中添加了以下代码

<?xml version="1.0" encoding="utf-8"?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms" 
    xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
    xmlns:local="clr-namespace:ListViewDemo;assembly=ListViewDemo" 
    x:Class="ListViewDemo.ListViewDemoPage"
>
    <ListView ItemsSource="{x:Static local:NamedColor.All}" />
</ContentPage>

但在运行时我得到类型未找到异常（请参阅下面的错误屏幕截图）

谁能建议我作为初学者做错了什么？

下面是我的NamedColor.cs文件代码

   using System;
using System.Collections.Generic;
using System.Reflection;
using System.Text;
using Xamarin.Forms;

namespace ListViewDemo
{
    public class NamedColor
    {
        // Instance members.
        private NamedColor()
        {
        }

        public string Name { private set; get; }

        public string FriendlyName { private set; get; }

        public Color Color { private set; get; }

        // Static members.
        static NamedColor()
        {
            List<NamedColor> all = new List<NamedColor>();
            StringBuilder stringBuilder = new StringBuilder();

            // Loop through the public static fields of type Color.
            foreach (FieldInfo fieldInfo in 
                            typeof (NamedColor).GetRuntimeFields ())
            {
                if (fieldInfo.IsPublic &&
                    fieldInfo.IsStatic &&
                    fieldInfo.FieldType == typeof (Color))
                {
                    // Convert the name to a friendly name.
                    string name = fieldInfo.Name;
                    stringBuilder.Clear();
                    int index = 0;

                    foreach (char ch in name)
                    {
                        if (index != 0 && Char.IsUpper(ch))
                        {
                            stringBuilder.Append(' ');
                        }
                        stringBuilder.Append(ch);
                        index++;
                    }

                    // Instantiate a NamedColor object.
                    NamedColor namedColor = new NamedColor
                    {
                        Name = name,
                        FriendlyName = stringBuilder.ToString(),
                        Color = (Color)fieldInfo.GetValue(null)
                    };

                    // Add it to the collection.
                    all.Add(namedColor);
                }
            }
            all.TrimExcess();
            All = all;
        }

        public static IEnumerable<NamedColor> All { private set; get; }

        // Color names and definitions from http://www.w3.org/TR/css3-color/
        // (but with color names converted to camel case).
        public static readonly Color AliceBlue = Color.FromRgb(240, 248, 255);
        public static readonly Color AntiqueWhite = Color.FromRgb(250, 235, 215);
        public static readonly Color Aqua = Color.FromRgb(0, 255, 255);
        public static readonly Color Aquamarine = Color.FromRgb(127, 255, 212);
        public static readonly Color Azure = Color.FromRgb(240, 255, 255);
        public static readonly Color Beige = Color.FromRgb(245, 245, 220);
        public static readonly Color Bisque = Color.FromRgb(255, 228, 196);
        public static readonly Color Black = Color.FromRgb(0, 0, 0);
        public static readonly Color BlanchedAlmond = Color.FromRgb(255, 235, 205);
        public static readonly Color Blue = Color.FromRgb(0, 0, 255);
        public static readonly Color BlueViolet = Color.FromRgb(138, 43, 226);
        public static readonly Color Brown = Color.FromRgb(165, 42, 42);
        public static readonly Color Burlywood = Color.FromRgb(222, 184, 135);
        public static readonly Color CadetBlue = Color.FromRgb(95, 158, 160);
        public static readonly Color Chartreuse = Color.FromRgb(127, 255, 0);
        public static readonly Color Chocolate = Color.FromRgb(210, 105, 30);
        public static readonly Color Coral = Color.FromRgb(255, 127, 80);
        public static readonly Color CornflowerBlue = Color.FromRgb(100, 149, 237);
        public static readonly Color Cornsilk = Color.FromRgb(255, 248, 220);
        public static readonly Color Crimson = Color.FromRgb(220, 20, 60);
        public static readonly Color Cyan = Color.FromRgb(0, 255, 255);
        public static readonly Color DarkBlue = Color.FromRgb(0, 0, 139);
        public static readonly Color DarkCyan = Color.FromRgb(0, 139, 139);
        public static readonly Color DarkGoldenrod = Color.FromRgb(184, 134, 11);
        public static readonly Color DarkGray = Color.FromRgb(169, 169, 169);
        public static readonly Color DarkGreen = Color.FromRgb(0, 100, 0);
        public static readonly Color DarkGrey = Color.FromRgb(169, 169, 169);
        public static readonly Color DarkKhaki = Color.FromRgb(189, 183, 107);
        public static readonly Color DarkMagenta = Color.FromRgb(139, 0, 139);
        public static readonly Color DarkOliveGreen = Color.FromRgb(85, 107, 47);
        public static readonly Color DarkOrange = Color.FromRgb(255, 140, 0);
        public static readonly Color DarkOrchid = Color.FromRgb(153, 50, 204);
        public static readonly Color DarkRed = Color.FromRgb(139, 0, 0);
        public static readonly Color DarkSalmon = Color.FromRgb(233, 150, 122);
        public static readonly Color DarkSeaGreen = Color.FromRgb(143, 188, 143);
        public static readonly Color DarkSlateBlue = Color.FromRgb(72, 61, 139);
        public static readonly Color DarkSlateGray = Color.FromRgb(47, 79, 79);
        public static readonly Color DarkSlateGrey = Color.FromRgb(47, 79, 79);
        public static readonly Color DarkTurquoise = Color.FromRgb(0, 206, 209);
        public static readonly Color DarkViolet = Color.FromRgb(148, 0, 211);
        public static readonly Color DeepPink = Color.FromRgb(255, 20, 147);
        public static readonly Color DeepSkyBlue = Color.FromRgb(0, 191, 255);
        public static readonly Color DimGray = Color.FromRgb(105, 105, 105);
        public static readonly Color DimGrey = Color.FromRgb(105, 105, 105);
        public static readonly Color DodgerBlue = Color.FromRgb(30, 144, 255);
        public static readonly Color Firebrick = Color.FromRgb(178, 34, 34);
        public static readonly Color FloralWhite = Color.FromRgb(255, 250, 240);
        public static readonly Color ForestGreen = Color.FromRgb(34, 139, 34);
        public static readonly Color Fuchsia = Color.FromRgb(255, 0, 255);
        public static readonly Color Gainsboro = Color.FromRgb(220, 220, 220);
        public static readonly Color GhostWhite = Color.FromRgb(248, 248, 255);
        public static readonly Color Gold = Color.FromRgb(255, 215, 0);
        public static readonly Color Goldenrod = Color.FromRgb(218, 165, 32);
        public static readonly Color Gray = Color.FromRgb(128, 128, 128);
        public static readonly Color Green = Color.FromRgb(0, 128, 0);
        public static readonly Color GreenYellow = Color.FromRgb(173, 255, 47);
        public static readonly Color Grey = Color.FromRgb(128, 128, 128);
        public static readonly Color Honeydew = Color.FromRgb(240, 255, 240);
        public static readonly Color HotPink = Color.FromRgb(255, 105, 180);
        public static readonly Color IndianRed = Color.FromRgb(205, 92, 92);
        public static readonly Color Indigo = Color.FromRgb(75, 0, 130);
        public static readonly Color Ivory = Color.FromRgb(255, 255, 240);
        public static readonly Color Khaki = Color.FromRgb(240, 230, 140);
        public static readonly Color Lavender = Color.FromRgb(230, 230, 250);
        public static readonly Color LavenderBlush = Color.FromRgb(255, 240, 245);
        public static readonly Color LawnGreen = Color.FromRgb(124, 252, 0);
        public static readonly Color LemonChiffon = Color.FromRgb(255, 250, 205);
        public static readonly Color LightBlue = Color.FromRgb(173, 216, 230);
        public static readonly Color LightCoral = Color.FromRgb(240, 128, 128);
        public static readonly Color LightCyan = Color.FromRgb(224, 255, 255);
        public static readonly Color LightGoldenrodYellow = Color.FromRgb(250, 250, 210);
        public static readonly Color LightGray = Color.FromRgb(211, 211, 211);
        public static readonly Color LightGreen = Color.FromRgb(144, 238, 144);
        public static readonly Color LightGrey = Color.FromRgb(211, 211, 211);
        public static readonly Color LightPink = Color.FromRgb(255, 182, 193);
        public static readonly Color LightSalmon = Color.FromRgb(255, 160, 122);
        public static readonly Color LightSeaGreen = Color.FromRgb(32, 178, 170);
        public static readonly Color LightSkyBlue = Color.FromRgb(135, 206, 250);
        public static readonly Color LightSlateGray = Color.FromRgb(119, 136, 153);
        public static readonly Color LightSlateGrey = Color.FromRgb(119, 136, 153);
        public static readonly Color LightSteelBlue = Color.FromRgb(176, 196, 222);
        public static readonly Color LightYellow = Color.FromRgb(255, 255, 224);
        public static readonly Color Lime = Color.FromRgb(0, 255, 0);
        public static readonly Color LimeGreen = Color.FromRgb(50, 205, 50);
        public static readonly Color Linen = Color.FromRgb(250, 240, 230);
        public static readonly Color Magenta = Color.FromRgb(255, 0, 255);
        public static readonly Color Maroon = Color.FromRgb(128, 0, 0);
        public static readonly Color MediumAquamarine = Color.FromRgb(102, 205, 170);
        public static readonly Color MediumBlue = Color.FromRgb(0, 0, 205);
        public static readonly Color MediumOrchid = Color.FromRgb(186, 85, 211);
        public static readonly Color MediumPurple = Color.FromRgb(147, 112, 219);
        public static readonly Color MediumSeaGreen = Color.FromRgb(60, 179, 113);
        public static readonly Color MediumSlateBlue = Color.FromRgb(123, 104, 238);
        public static readonly Color MediumSpringGreen = Color.FromRgb(0, 250, 154);
        public static readonly Color MediumTurquoise = Color.FromRgb(72, 209, 204);
        public static readonly Color MediumVioletRed = Color.FromRgb(199, 21, 133);
        public static readonly Color MidnightBlue = Color.FromRgb(25, 25, 112);
        public static readonly Color MintCream = Color.FromRgb(245, 255, 250);
        public static readonly Color MistyRose = Color.FromRgb(255, 228, 225);
        public static readonly Color Moccasin = Color.FromRgb(255, 228, 181);
        public static readonly Color NavajoWhite = Color.FromRgb(255, 222, 173);
        public static readonly Color Navy = Color.FromRgb(0, 0, 128);
        public static readonly Color OldLace = Color.FromRgb(253, 245, 230);
        public static readonly Color Olive = Color.FromRgb(128, 128, 0);
        public static readonly Color OliveDrab = Color.FromRgb(107, 142, 35);
        public static readonly Color Orange = Color.FromRgb(255, 165, 0);
        public static readonly Color OrangeRed = Color.FromRgb(255, 69, 0);
        public static readonly Color Orchid = Color.FromRgb(218, 112, 214);
        public static readonly Color PaleGoldenrod = Color.FromRgb(238, 232, 170);
        public static readonly Color PaleGreen = Color.FromRgb(152, 251, 152);
        public static readonly Color PaleTurquoise = Color.FromRgb(175, 238, 238);
        public static readonly Color PaleVioletRed = Color.FromRgb(219, 112, 147);
        public static readonly Color PapayaWhip = Color.FromRgb(255, 239, 213);
        public static readonly Color PeachPuff = Color.FromRgb(255, 218, 185);
        public static readonly Color Peru = Color.FromRgb(205, 133, 63);
        public static readonly Color Pink = Color.FromRgb(255, 192, 203);
        public static readonly Color Plum = Color.FromRgb(221, 160, 221);
        public static readonly Color PowderBlue = Color.FromRgb(176, 224, 230);
        public static readonly Color Purple = Color.FromRgb(128, 0, 128);
        public static readonly Color Red = Color.FromRgb(255, 0, 0);
        public static readonly Color RosyBrown = Color.FromRgb(188, 143, 143);
        public static readonly Color RoyalBlue = Color.FromRgb(65, 105, 225);
        public static readonly Color SaddleBrown = Color.FromRgb(139, 69, 19);
        public static readonly Color Salmon = Color.FromRgb(250, 128, 114);
        public static readonly Color SandyBrown = Color.FromRgb(244, 164, 96);
        public static readonly Color SeaGreen = Color.FromRgb(46, 139, 87);
        public static readonly Color SeaShell = Color.FromRgb(255, 245, 238);
        public static readonly Color Sienna = Color.FromRgb(160, 82, 45);
        public static readonly Color Silver = Color.FromRgb(192, 192, 192);
        public static readonly Color SkyBlue = Color.FromRgb(135, 206, 235);
        public static readonly Color SlateBlue = Color.FromRgb(106, 90, 205);
        public static readonly Color SlateGray = Color.FromRgb(112, 128, 144);
        public static readonly Color SlateGrey = Color.FromRgb(112, 128, 144);
        public static readonly Color Snow = Color.FromRgb(255, 250, 250);
        public static readonly Color SpringGreen = Color.FromRgb(0, 255, 127);
        public static readonly Color SteelBlue = Color.FromRgb(70, 130, 180);
        public static readonly Color Tan = Color.FromRgb(210, 180, 140);
        public static readonly Color Teal = Color.FromRgb(0, 128, 128);
        public static readonly Color Thistle = Color.FromRgb(216, 191, 216);
        public static readonly Color Tomato = Color.FromRgb(255, 99, 71);
        public static readonly Color Turquoise = Color.FromRgb(64, 224, 208);
        public static readonly Color Violet = Color.FromRgb(238, 130, 238);
        public static readonly Color Wheat = Color.FromRgb(245, 222, 179);
        public static readonly Color White = Color.FromRgb(255, 255, 255);
        public static readonly Color WhiteSmoke = Color.FromRgb(245, 245, 245);
        public static readonly Color Yellow = Color.FromRgb(255, 255, 0);
        public static readonly Color YellowGreen = Color.FromRgb(154, 205, 50);
    }
}

【问题讨论】：

请显示NamedColor的定义。它是否在同一个程序集中和ListViewDemo 命名空间中？如果命名空间不同，例如； ListViewDemo.Colors 那么你应该在你的local 定义中拥有它，比如：xmlns:local="clr-namespace:ListViewDemo.Colors;assembly=ListViewDemo"
@GeraldVersluis 我已经编辑了我的问题并添加了 NamedColor.cs 代码。请参阅编辑后的代码。两者都在同一个名称空间“ListViewDemo”中
他们是否也在同一个项目中？
@GeraldVersluis 是的，所有文件都在同一个项目中。
那我看不出有什么理由让它不起作用。然而，有一件事引起了我的注意；在屏幕截图中它说在 xmlns 中找不到它。如果它是在寻找本地的，我认为应该在错误消息中提到它。虽然不是 100% 确定.. 确保你清理并重建一切。有什么方法可以让我看看你的代码吗？

标签： xamarin xamarin.forms

【解决方案1】：

我有时注意到，当一个类仅在 XAML 中引用时，链接器会将其从最终应用程序中剥离。我通过添加类似于以下内容来强制它包含它：

private void _forceLinking() {
    var unused = new Full.Namespace.NamedColor();
}

在我的App.xaml.cs 课堂上。可能有更好的方法来做到这一点，但至少这对我有效并解决了这个问题。

【讨论】：