Custom extension method to simplify LINQ to SQL statement

Question

I have a snippet of LINQ code that I need to use in a lot of queries

let catchmentId = Convert.ToInt32(
        phy.PhysicalProperty_binData.Substring(offset + 3         


        

Answer 1

Wrong language (sorry) here it is in F# if people need.

let catchmentId =  
    // Curry in invariant components.
    let newSubstr end = 
        phy.PhysicalProperty_binData.Substring(offset + end, 1)
    Convert.ToInt32(
        newSubstr 3 +
        newSubstr 2 + 
        newSubstr 1 +
        newSubstr 0)

Answer 2

You can map custom SQL functions in your Entity model.

http://msdn.microsoft.com/en-us/library/dd456812(v=vs.103).aspx

Answer 3

The links on this page will show you how you can use custom attributes to tie your extension method to a user-defined function in your database.

Of course, that will mean that you need to create a user-defined function in SQL to do the same logic that your extension method wants to do.

Another option is to have your extension method produce an Expression, and use LINQKit to parse through the query tree, finding the call to .Compile() off of that expression, and inlining that expression in the query.