我今天遇到了同样的问题。基于内部异常，似乎报表查看器需要获得相关dll的版本才能正常工作。如果dll是嵌入式的，报表查看器无法找到它。

System.ArgumentException: The path is not of a legal form.
   at System.IO.Path.NewNormalizePath(String path, Int32 maxPathLength, Boolean expandShortPaths)
   at System.IO.Path.NormalizePath(String path, Boolean fullCheck, Int32 maxPathLength, Boolean expandShortPaths)
   at System.IO.Path.GetFullPathInternal(String path)
   at System.IO.Path.GetFullPath(String path)
   at System.Diagnostics.FileVersionInfo.GetFullPathWithAssert(String fileName)
   at System.Diagnostics.FileVersionInfo.GetVersionInfo(String fileName)
   at Microsoft.ReportingServices.ReportIntermediateFormat.Persistence.IntermediateFormatVersion.<>c__DisplayClass2_0.<.cctor>b__0()
   at Microsoft.ReportingServices.Diagnostics.RevertImpersonationContext.<>c__DisplayClass1_0.<Run>b__0(Object state)
   at System.Security.SecurityContext.Run(SecurityContext securityContext, ContextCallback callback, Object state)
   at Microsoft.ReportingServices.Diagnostics.RevertImpersonationContext.Run(ContextBody callback)
   at Microsoft.ReportingServices.ReportIntermediateFormat.Persistence.IntermediateFormatVersion..cctor()
   --- End of inner exception stack trace ---

经过反复试验，我发现要使报表查看器正常工作，需要从Fody/Costura中排除“Microsoft.ReportViewer.ProcessingObjectModel”和“Microsoft.ReportViewer.Common”。以下是我正在使用的FodyWeavers.xml。

<?xml version="1.0" encoding="utf-8"?>
<Weavers xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="FodyWeavers.xsd">
  <Costura>
    <ExcludeAssemblies>
      Microsoft.ReportViewer.ProcessingObjectModel
      Microsoft.ReportViewer.Common
    </ExcludeAssemblies>
  </Costura>
</Weavers>