阅读了这里张贴的所有解决方案后。我就是这样解决的：

// How to embedded a "Text file" inside of a C# project
//   and read it as a resource from c# code:
//
// (1) Add Text File to Project.  example: 'myfile.txt'
//
// (2) Change Text File Properties:
//      Build-action: EmbeddedResource
//      Logical-name: myfile.txt      
//          (note only 1 dot permitted in filename)
//
// (3) from c# get the string for the entire embedded file as follows:
//
//     string myfile = GetEmbeddedResourceFile("myfile.txt");

public static string GetEmbeddedResourceFile(string filename) {
    var a = System.Reflection.Assembly.GetExecutingAssembly();
    using (var s = a.GetManifestResourceStream(filename))
    using (var r = new System.IO.StreamReader(s))
    {
        string result = r.ReadToEnd();
        return result;
    }
    return "";      
}

我刚才了解到，文件名中不允许有“.”（点）。

Templates.plainMailBodyTemplate-en.txt-->工作！！！Templates.plainMailBodyTemplate.en.txt-->无法通过GetManifestResourceStream（）工作

可能是因为框架混淆了名称空间和文件名。。。

如SonarCloud所示，更好的做法是：

public class Example
{
    public static void Main()
    { 
        // Compliant: type of the current class
        Assembly assembly = typeof(Example).Assembly; 
        Console.WriteLine("Assembly name: {0}", assem.FullName);

        // Non-compliant
        Assembly assembly = Assembly.GetExecutingAssembly();
        Console.WriteLine("Assembly name: {0}", assem.FullName);
    }
}

我知道这已经过时了，但我只是想指出，对于NETMF（.Net MicroFramework），您可以轻松做到这一点：

string response = Resources.GetString(Resources.StringResources.MyFileName);

由于NETMF没有GetManifestResourceStream

读取表单加载事件上的嵌入式TXT文件。

动态设置变量。

string f1 = "AppName.File1.Ext";
string f2 = "AppName.File2.Ext";
string f3 = "AppName.File3.Ext";

呼叫Try Catch。

try 
{
     IncludeText(f1,f2,f3); 
     /// Pass the Resources Dynamically 
     /// through the call stack.
}

catch (Exception Ex)
{
     MessageBox.Show(Ex.Message);  
     /// Error for if the Stream is Null.
}

为IncludeText（）创建Void，Visual Studio将为您完成此操作。单击灯泡以自动生成代码块。

将以下内容放入生成的代码块中

资源1

var assembly = Assembly.GetExecutingAssembly();
using (Stream stream = assembly.GetManifestResourceStream(file1))
using (StreamReader reader = new StreamReader(stream))
{
string result1 = reader.ReadToEnd();
richTextBox1.AppendText(result1 + Environment.NewLine + Environment.NewLine );
}

资源2

var assembly = Assembly.GetExecutingAssembly();
using (Stream stream = assembly.GetManifestResourceStream(file2))
using (StreamReader reader = new StreamReader(stream))
{
string result2 = reader.ReadToEnd();
richTextBox1.AppendText(
result2 + Environment.NewLine + 
Environment.NewLine );
}

资源3

var assembly = Assembly.GetExecutingAssembly();
using (Stream stream = assembly.GetManifestResourceStream(file3))

using (StreamReader reader = new StreamReader(stream))
{
    string result3 = reader.ReadToEnd();
    richTextBox1.AppendText(result3);
}

如果您希望将返回的变量发送到其他地方，只需调用另一个函数并。。。

using (StreamReader reader = new StreamReader(stream))
{
    string result3 = reader.ReadToEnd();
    ///richTextBox1.AppendText(result3);
    string extVar = result3;

    /// another try catch here.

   try {

   SendVariableToLocation(extVar)
   {
         //// Put Code Here.
   }

       }

  catch (Exception ex)
  {
    Messagebox.Show(ex.Message);
  }

}

这是一种将多个txt文件合并并在单个富文本框中读取其嵌入数据的方法。这是我期望的代码示例的效果。

这是一个类，您可能会发现从当前程序集读取嵌入式资源文件非常方便：

using System.IO;
using System.Linq;
using System.Text;
using System.Reflection;

public static class EmbeddedResourceUtils
{
    public static string ReadFromResourceFile(string endingFileName)
    {
        var assembly = Assembly.GetExecutingAssembly();
        var manifestResourceNames = assembly.GetManifestResourceNames();

        foreach (var resourceName in manifestResourceNames)
        {
            var fileNameFromResourceName = _GetFileNameFromResourceName(resourceName);
            if (!fileNameFromResourceName.EndsWith(endingFileName))
            {
                continue;
            }

            using (var manifestResourceStream = assembly.GetManifestResourceStream(resourceName))
            {
                if (manifestResourceStream == null)
                {
                    continue;
                }

                using (var streamReader = new StreamReader(manifestResourceStream))
                {
                    return streamReader.ReadToEnd();
                }
            }
        }

        return null;
    }
    
    // https://stackoverflow.com/a/32176198/3764804
    private static string _GetFileNameFromResourceName(string resourceName)
    {
        var stringBuilder = new StringBuilder();
        var escapeDot = false;
        var haveExtension = false;

        for (var resourceNameIndex = resourceName.Length - 1;
            resourceNameIndex >= 0;
            resourceNameIndex--)
        {
            if (resourceName[resourceNameIndex] == '_')
            {
                escapeDot = true;
                continue;
            }

            if (resourceName[resourceNameIndex] == '.')
            {
                if (!escapeDot)
                {
                    if (haveExtension)
                    {
                        stringBuilder.Append('\\');
                        continue;
                    }

                    haveExtension = true;
                }
            }
            else
            {
                escapeDot = false;
            }

            stringBuilder.Append(resourceName[resourceNameIndex]);
        }

        var fileName = Path.GetDirectoryName(stringBuilder.ToString());
        return fileName == null ? null : new string(fileName.Reverse().ToArray());
    }
}