Dynamic OrderBy in a LINQ query

[Joseph S.]

Hello,

I need to build a dynamic LINQ query (VB.NET) where the sort field must be build as string at runtime. My query is like this:

Dim lobjQueryGenData As IQueryable(Of clsDmlEO) = From GenData In ObjectScope.Extent(Of clsDmlEO)() Select GenData Where GenData.SessionId = pstrSessionId

lobjQueryGenData = lobjQueryGenData.OrderBy(Function(GenData) GenData.RowId)

clsDmlEO is a "<Telerik.OpenAccess.Persistent()> <Serializable()>" class mapped to SQL Server table.

I need to change the OrderBy in something like this:

lobjQueryGenData = lobjQueryGenData.OrderBy(pstrSortField)

where pstrSortField is a string variabile/parameter built at runtime.

Please can you help me?

[Simeon Simeonov]

Hello Joseph,

Thank you for contacting us.

What you need is easily accomplished using Microsoft's Dynamic Query Library together with Open Access. There is a blog post discussing the topic here.

What you need to do is add to your project the Microsoft's DynamicQuery NuGet package. You can find it by searching for "DynamicQuery" or "Dynamic Expression Api" in the NuGet package manager.

I have prepared example for ordering some forum posts by "Id" or by "DateCreated":

Imports Forum.Data
Imports System.Linq.Dynamic

Namespace Example
    Class TestMain
        Private Shared Sub Main(args As String())
            Using context = New ForumFluentModel()
                Dim orderedForumPostsById = context.ForumPosts.OrderBy("Id")
                Dim orderedForumPostsDateCreated = context.ForumPosts.OrderBy("DateCreated")
            End Using
        End Sub
    End Class
End Namespace

Please note the imported System.Linq.Dynamic namespace. You will need this because in it is the class holding the OrderBy extension method of IQueryable you need.

I hope you find this information helpful.

Regards,
Simeon Simeonov
Telerik