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InfoQ Homepage News Wrapping Stored Procedures in .NET Languages

Wrapping Stored Procedures in .NET Languages

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.

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