There are some errors about using ant build c# project

[Fung Yun]

Hi, All

Here is my build.xml:

<target name= "build.ECCWS">
<solution configuration="release" solutionfile="C:\Hudson-slave\staging\ECCSource\ECCWS\ECCWS.sln" />
</target>

But after "ant build.ECCWS"in cmd window, and have a error result:
Problem:failed to create task or type solution
Cause: The name is undefined
Action: Check thr spelling
Action: Check that any custom tasks/types have been declared
Action: Check that any <presetdef><macrodef>declarations have taken palce.

So, how can I sloved it?

Many thanks

Fung yun