Создал иерархию папок для классов и интерфейсов типа *Signal*

Signal Generator/Signal Generator.csproj

@@ -58,11 +58,11 @@
     <Compile Include="AddSignalWindow.xaml.cs">
       <DependentUpon>AddSignalWindow.xaml</DependentUpon>
     </Compile>
-    <Compile Include="AnalogSignalMethods.cs" />
-    <Compile Include="FmSignal.cs" />
+    <Compile Include="Signal\Base\AnalogSignalMethods.cs" />
+    <Compile Include="Signal\FmSignal.cs" />
     <Compile Include="Settings.cs" />
-    <Compile Include="Parameter.cs" />
-    <Compile Include="SinusoidalSignal.cs" />
+    <Compile Include="Signal\Base\Parameter.cs" />
+    <Compile Include="Signal\SinusoidalSignal.cs" />
     <Compile Include="TaskWindow.xaml.cs">
       <DependentUpon>TaskWindow.xaml</DependentUpon>
     </Compile>
@@ -78,7 +78,7 @@
       <DependentUpon>App.xaml</DependentUpon>
       <SubType>Code</SubType>
     </Compile>
-    <Compile Include="IAnalogSignal.cs" />
+    <Compile Include="Signal\Base\IAnalogSignal.cs" />
     <Compile Include="MainWindow.xaml.cs">
       <DependentUpon>MainWindow.xaml</DependentUpon>
       <SubType>Code</SubType>
@@ -89,7 +89,7 @@
     </Page>
   </ItemGroup>
   <ItemGroup>
-    <Compile Include="MultiSignal.cs" />
+    <Compile Include="Signal\MultiSignal.cs" />
     <Compile Include="Properties\AssemblyInfo.cs">
       <SubType>Code</SubType>
     </Compile>

Signal Generator/AnalogSignalMethods.cs → Signal Generator/Signal/Base/AnalogSignalMethods.cs

@@ -9,7 +9,7 @@ namespace Signal_Generator
 {
     class AnalogSignalMethods
     {
-        internal string paramsToString(Collection<Parameter> paramsCollection)
+        protected string paramsToString(Collection<Parameter> paramsCollection)
         {
             string result = "";
             foreach (Parameter p in paramsCollection)