MSBuild and creating ZIP files

Here is my build script:

<?xml version="1.0" encoding="utf-8" ?>
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <Import Project="$(MSBuildExtensionsPath)\MSBuildCommunityTasks\MSBuild.Community.Tasks.Targets"/>
  <PropertyGroup>
    <!-- Path where the solution file is located (.sln) -->
    <ProjectPath>W:\Demo</ProjectPath>
    <!-- Location of compiled files -->
    <DebugPath>W:\Demo\bin\Debug</DebugPath>
    <ReleasePath>W:\Demo\bin\Release</ReleasePath>
    <!-- Name of the solution to be compiled without the .sln extension -->         <ProjectSolutionName>DemoTool</ProjectSolutionName>

    <!-- Path where the nightly zip file will be copyd -->
    <NightlyBuildPath>W:\Nightly_Builds\Demo</NightlyBuildPath>
    <!-- Name of the nighly zip file (YYYYMMDD_NightlyZipName.zip, date added automatically) -->
    <NightlyZipName>Demo</NightlyZipName>
  </PropertyGroup>

  <ItemGroup>
    <!-- All files and folders from ./bin/Debug or ./bin/Release what will be added to the nightly zip -->
    <DebugApplicationFiles Include="$(DebugPath)\**\*.*" Exclude="$(DebugPath)\*vshost.exe*" />
    <ReleaseApplicationFiles Include="$(ReleasePath)\**\*.*" Exclude="$(ReleasePath)\*vshost.exe*" />
  </ItemGroup>

  <Target Name="DebugBuild">
    <Message Text="Building $(ProjectSolutionName) Debug Build" />
    <MSBuild Projects="$(ProjectPath)\$(ProjectSolutionName).sln" Targets="Clean" Properties="Configuration=Debug"/>
    <MSBuild Projects="$(ProjectPath)\$(ProjectSolutionName).sln" Targets="Build" Properties="Configuration=Debug"/>
    <Message Text="$(ProjectSolutionName) Debug Build Complete!" />
    <CallTarget Targets="CreateNightlyZip" />
  </Target>

  <Target Name="CreateNightlyZip">
    <PropertyGroup>
      <StringDate>$([System.DateTime]::Now.ToString('yyyyMMdd'))</StringDate>
    </PropertyGroup>
    <MakeDir Directories="$(NightlyBuildPath)"/>
    <Zip Files="@(DebugApplicationFiles)"
          WorkingDirectory="$(DebugPath)"
          ZipFileName="$(NightlyBuildPath)\$(StringDate)_$(NightlyZipName).zip"
          ZipLevel="9" />
  </Target>
</Project>

My script works perfectly, only there is one strange problem. When i build a project first time and there is no \bin\Debug folder and its created during the build, but the ZIP file still comes empty. Running the build script second time when the \bin\Debug folder is now in place with builded files then the file are added to the ZIP.

What could be the problem that running script first time the ZIP file is empty?

The problem is in the DebugApplicationFiles item collection. It is created before the build is invoked. Move the DebugApplicationFiles into CreateNightlyZip target. Update your script this way:

<Target Name="CreateNightlyZip">
    <PropertyGroup>
      <StringDate>$([System.DateTime]::Now.ToString('yyyyMMdd'))</StringDate>
    </PropertyGroup>
    <ItemGroup>
        <DebugApplicationFiles Include="$(DebugPath)\**\*.*" Exclude="$(DebugPath)\*vshost.exe*" />
    </ItemGroup>
    <MakeDir Directories="$(NightlyBuildPath)"/>
    <Zip Files="@(DebugApplicationFiles)"
      WorkingDirectory="$(DebugPath)"
      ZipFileName="$(NightlyBuildPath)\$(StringDate)_$(NightlyZipName).zip"
      ZipLevel="9" />
</Target>