BT

Facilitating the Spread of Knowledge and Innovation in Professional Software Development

Write for InfoQ

Topics

Choose your language

InfoQ Homepage News Wrapping Stored Procedures in .NET Languages

Wrapping Stored Procedures in .NET Languages

Bookmarks

Creating wrapper functions for pre-existing stored procedures is surprisingly difficult in .NET. Stored procedures have certain calling conventions that aren’t generally used in the .NET Framework. These include:

  • Pass by Reference Parameters
  • Output Parameters
  • Optional Parameters with default values
  • All parameters are nullable

Until recently, full mappings were not possible. C# doesn’t currently support optional parameters, making placeholders for missing parameters necessary. VB could handle optional parameters, but not if those parameters were also nullable. For example, you cannot write:

Function FindCustomer(Optional ByVal firstName As String = Nothing, _ 
Optional ByVal lastName As String = Nothing, _
Optional ByVal zipCode As Integer? = Nothing) As DataTable

 This becomes a real concern when call search-style stored procedures that then to have numerous optional parameters. With C# 4 and VB 10, the last of these holes have been addressed. C# now supports optional values and both languages can use optional types in conjunction with nullable structures.

Feature

C#

Mapping

VB

Mapping

F#

Mapping

Pass by Reference

1

ref type [param]

7

ByRef [param] As [type]

4

[param] : [type] byref

Output

1

out type [param]

7

ByRef [param] As [type]

4

[param] : [type] byref

Optional Strings

4

string param = [default]

7

Optional [param] As String = [default]

N/A

4

Normal functions do not support optional parameters.

Method functions use: ?[param] : [type]

Optional (other)

4

[type] param = [default]

7

Optional param As [type] = [default]

Nullable Strings

1

string param

7

param as String

4

[param] : string

[param] : string option

Nullable (other)

2

[type]? param

8

param As Nullable(of

[type])

4

[param] : Nullable<[type]>

[param] : [type] option

9

param as [type]?

Optional Nullable (other)

4

[type]? param = [default]

10

Optional param As [type]? = [default]

4

?[param] : Nullable<[type]>

?[param] : [type] option

It should be noted that while F# does support returning multiple values, the support is very limited. There is no way to update more than one arbitrary mutable value without using the byref syntax.

Rate this Article

Adoption
Style

BT