The buildType parameter is optional here. If buildtype is null/empty the complete list of builds in the given teamProject is returned; otherwise, the builds would be filtered based on the given buildtype.
Namespace:  Microsoft.TeamFoundation.Build.Server.Compatibility
Assembly:  Microsoft.TeamFoundation.Build.Server (in Microsoft.TeamFoundation.Build.Server.dll)
Syntax
'Declaration
<WebMethodAttribute> _
Public Function GetListOfBuilds ( _
    teamProject As String, _
    buildType As String _
) As BuildData()
[WebMethodAttribute]
public BuildData[] GetListOfBuilds(
    string teamProject,
    string buildType
)
[WebMethodAttribute]
public:
array<BuildData^>^ GetListOfBuilds(
    String^ teamProject, 
    String^ buildType
)
[<WebMethodAttribute>]
member GetListOfBuilds : 
        teamProject:string * 
        buildType:string -> BuildData[] 
public function GetListOfBuilds(
    teamProject : String, 
    buildType : String
) : BuildData[]
Parameters
- teamProject
 Type: System.String
- buildType
 Type: System.String
Return Value
Type: array<Microsoft.TeamFoundation.Build.Server.Compatibility.BuildData[]
.NET Framework Security
- Full trust for the immediate caller. This member cannot be used by partially trusted code. For more information, see Using Libraries from Partially Trusted Code.
See Also
Reference
Microsoft.TeamFoundation.Build.Server.Compatibility Namespace