Using project references as assembly paths in T4

Question

I have a .tt script that needs to reference a couple of external assemblies.

Is it possible for the T4 host to automatically include the assemblies referenced in the project - rather than me manually adding an assembly directive for each one?

E.g. Referencing an assembly from a nuget is a moving target when using a path relative to $(ProjecDir).

Using assembly paths like $(Project)\bin\Debug\Example.dll also seems less than optimal - as it requires the build to have been successful previously - which is probably not the case if you have a .tt file generating the "ErrorGeneratingOutput" in a .cs file!?

Update 1:

So I have had a second stab at this but this time trying to tackle the issue around "TransformOnBuild" ( as a side note I can highly recommend @kzu's excellent project: https://github.com/clariuslabs/TransformOnBuild) and not having $(SolutionDir) available when not running TextTransform via direct from msbuild. Anyway - I came up with a 2-step solution.

1. msbuild target uses WriteLinesToFile task to generates a .tt file with a fresh list of assembly directives based on the references found in the csproj file.

2. Any other .tt files in the project can the include the auto-generated file to get project assemblies registered.

Here is an example of the target:

<Target Name="Write_AssemblyRefs_TT" BeforeTargets="TransformOnBuild">
  <!-- A message for all to enjoy! -->
  <WriteLinesToFile File="@(MyTextFile)" 
    Lines="&lt;# /* AUTOGENERATED BY MSBUILD and Kern Herskind Nightingale */ #&gt;" 
    Overwrite="true" 
    Encoding="Unicode" />
  <!-- Output all assembly references with a HintPath -->
  <WriteLinesToFile File="@(MyTextFile)" 
    Lines="&lt;#@ assembly name=&quot;$(ProjectDir)%(Reference.HintPath)&quot; #&gt;" 
    Overwrite="false"
    Encoding="Unicode"
    Condition="'%(Reference.HintPath)' != ''" />
  <!-- Output all project references - this could fail with custom nameing/build output dirs  -->
  <WriteLinesToFile File="@(MyTextFile)" 
    Lines="&lt;#@ assembly name=&quot;$(ProjectDir)%(ProjectReference.RelativeDir)bin\$(Configuration)\%(ProjectReference.Name).dll&quot; #&gt;" 
    Overwrite="false"
    Encoding="Unicode" />
</Target>
<ItemGroup>
  <MyTextFile Include="AssemblyRefs.tt" />
</ItemGroup>

And how to include it in the T4 file (trivial):

<#@ include file="AssemblyRefs.tt" #>

Code generation for the code generator :)

Update 2:

I have created a Nuget package to make it easy to add the above assembly directive generation build target: https://www.nuget.org/packages/AssemblyReferencesTT/1.0.12

Answer 1

i would have posted this in comment if i could.

for the question: it is not possible to include the assemblies referenced in the project automatically, but you can limit the work you have to do.

if you see below link in suggestion number 1, you can use c# to define assembly code before it is read by the t4. which make it possible to read a directory with reflection and load each assembly there.so the question is where will your assembly be ?

List<Assembly> allAssemblies = new List<Assembly>();
string path = Assembly.GetExecutingAssembly().Location;

foreach (string dll in Directory.GetFiles(path, "*.dll"))
    allAssemblies.Add(Assembly.LoadFile(dll));
    <#@ assembly name=dll #>

this is untested but should get you started at lest. for reference -> how to load all assemblies from within your /bin directory

for the second part:

1. using $(SolutionDir) but this is the same as the $(Project) one except one level lower. -> How do I use custom library/project in T4 text template?
2. use c# path utilities to navigate to the wanted path at runtime, but again this might require the assembly to compile first.
3. Registering the External Library in GAC. this seams to resolve your problem the most since you will not have to set a path at all. see -> How to register a .Net dll in GAC?

Edit: here is a working dynamic include. just reference the result of the .ttinclude generated by this in any other .tt file

i tested it with the debugger and it seems to work.

and change assembly localisation to point where you need it to.

<#@ template debug="false" hostspecific="false" language="C#" #>
<#@ assembly name="System.Core" #>
<#@ assembly name="System.Net.Http" #>
<#@ import namespace="System.Linq" #>
<#@ import namespace="System.Text" #>
<#@ import namespace="System.Collections.Generic" #>
<#@ import namespace="System.Reflection" #>
<#@ import namespace="System.IO" #>
<#@ output extension=".ttinclude" #><#

List<Assembly> allAssemblies = new List<Assembly>();
string file = Assembly.GetExecutingAssembly().Location;
if(file!= "")
{
    string path = Path.GetDirectoryName(file).TrimEnd();
    if(path != "")
        foreach (string dll in Directory.GetFiles(path, "*.dll"))
        {
            if(dll != "")
            {
                allAssemblies.Add(Assembly.LoadFile(dll));
                #>\<#<#= "@ assembly name=\""+ dll +"\" "#>\#><#="\n"#><#
            }
        }
}

#>

output:

<#@ assembly name="C:\TEMP\3mo0m0mq.dll" #> 
 <#@ assembly name="C:\TEMP\4ybsqre3.dll" #> 
 <#@ assembly name="C:\TEMP\ao0bzedf.dll" #> 
 <#@ assembly name="C:\TEMP\bo2w102t.dll" #> 
 <#@ assembly name="C:\TEMP\c5o2syvv.dll" #> 
 <#@ assembly name="C:\TEMP\dz1fin10.dll" #> 
 <#@ assembly name="C:\TEMP\giym0gef.dll" #> 
 <#@ assembly name="C:\TEMP\hjfgqkov.dll" #> 
 <#@ assembly name="C:\TEMP\ibuz4wvb.dll" #> 
 <#@ assembly name="C:\TEMP\ilrcwa2y.dll" #> 
 <#@ assembly name="C:\TEMP\k0yeumhb.dll" #> 
 <#@ assembly name="C:\TEMP\kirzdsqp.dll" #> 
 <#@ assembly name="C:\TEMP\ksxl4f2z.dll" #> 
 <#@ assembly name="C:\TEMP\l4kja4ts.dll" #> 
 <#@ assembly name="C:\TEMP\ljgxkpo0.dll" #> 
 <#@ assembly name="C:\TEMP\lkvkmlct.dll" #> 
 <#@ assembly name="C:\TEMP\lnofhhlq.dll" #> 
 <#@ assembly name="C:\TEMP\nbqhmjqd.dll" #> 
 <#@ assembly name="C:\TEMP\oc3pxhmq.dll" #> 
 <#@ assembly name="C:\TEMP\qb43ntcu.dll" #> 
 <#@ assembly name="C:\TEMP\qlyoyhyr.dll" #> 
 <#@ assembly name="C:\TEMP\snwvtb00.dll" #> 
 <#@ assembly name="C:\TEMP\umhhb2wb.dll" #> 
 <#@ assembly name="C:\TEMP\xsyfel0b.dll" #> 
 <#@ assembly name="C:\TEMP\z1weyhko.dll" #> 

you can escape the <# character with \<# see this.