Creating a User-Defined Type
To create a user-defined type (UDT) capable of being installed in Microsoft SQL Server 2005, you must first create a class in one of the supported Microsoft .NET Framework programming languages, such as Microsoft Visual C# or Microsoft Visual Basic, which conforms to the specifications for creating UDTs. The class can then be compiled as a dynamic-link library (DLL), which can be loaded in SQL Server 2005. You can also create and deploy UDTs using Microsoft Visual Studio.
The ability to execute common language runtime (CLR) code is set to OFF by default in SQL Server 2005. The CLR can be enabled by using the sp_configure system stored procedure, as shown in the following Transact-SQL statements:
sp_configure 'clr enabled', 1
Reconfigure
For more information, see Working with CLR User-defined Types.
In This Section
- User-Defined Type Requirements
Describes the requirements for coding user-defined types.
- Coding User-Defined Types
Demonstrates coding techniques involved in creating user-defined types.
The following code listing defines the Point UDT, which is described in detail in Coding User-Defined Types.
The complete code listings for the other examples discussed in this section can be obtained by installing the CLR samples. For instructions on installing these samples, see Installing Samples.
C#
using System;
using System.Data;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
using System.Text;
[Serializable]
[Microsoft.SqlServer.Server.SqlUserDefinedType(Format.Native,
IsByteOrdered=true, ValidationMethodName = "ValidatePoint")]
public struct Point : INullable
{
private bool is_Null;
private Int32 _x;
private Int32 _y;
public bool IsNull
{
get
{
return (is_Null);
}
}
public static Point Null
{
get
{
Point pt = new Point();
pt.is_Null = true;
return pt;
}
}
// Use StringBuilder to provide string representation of UDT.
public override string ToString()
{
// Since InvokeIfReceiverIsNull defaults to 'true'
// this test is unneccesary if Point is only being called
// from SQL.
if (this.IsNull)
return "NULL";
else
{
StringBuilder builder = new StringBuilder();
builder.Append(_x);
builder.Append(",");
builder.Append(_y);
return builder.ToString();
}
}
[SqlMethod(OnNullCall = false)]
public static Point Parse(SqlString s)
{
// With OnNullCall=false, this check is unnecessary if
// Point only called from SQL.
if (s.IsNull)
return Null;
// Parse input string to separate out points.
Point pt = new Point();
string[] xy = s.Value.Split(",".ToCharArray());
pt.X = Int32.Parse(xy[0]);
pt.Y = Int32.Parse(xy[1]);
// Call ValidatePoint to enforce validation
// for string conversions.
if (!pt.ValidatePoint())
throw new ArgumentException("Invalid XY coordinate values.");
return pt;
}
// X and Y coordinates exposed as properties.
public Int32 X
{
get
{
return this._x;
}
// Call ValidatePoint to ensure valid range of Point values.
set
{
Int32 temp = _x;
_x = value;
if (!ValidatePoint())
{
_x = temp;
throw new ArgumentException("Invalid X coordinate value.");
}
}
}
public Int32 Y
{
get
{
return this._y;
}
set
{
Int32 temp = _y;
_y = value;
if (!ValidatePoint())
{
_y = temp;
throw new ArgumentException("Invalid Y coordinate value.");
}
}
}
// Validation method to enforce valid X and Y values.
private bool ValidatePoint()
{
// Allow only zero or positive integers for X and Y coordinates.
if ((_x >= 0) && (_y >= 0))
{
return true;
}
else
{
return false;
}
}
// Distance from 0 to Point method.
[SqlMethod(OnNullCall = false)]
public Double Distance()
{
return DistanceFromXY(0, 0);
}
// Distance from Point to the specified point method.
[SqlMethod(OnNullCall = false)]
public Double DistanceFrom(Point pFrom)
{
return DistanceFromXY(pFrom.X, pFrom.Y);
}
// Distance from Point to the specified x and y values method.
[SqlMethod(OnNullCall = false)]
public Double DistanceFromXY(Int32 iX, Int32 iY)
{
return Math.Sqrt(Math.Pow(iX - _x, 2.0) + Math.Pow(iY - _y, 2.0));
}
}
Visual Basic
Option Explicit On
Option Strict On
Imports System
Imports System.Data.SqlTypes
Imports Microsoft.SqlServer.Server
Imports System.Text
<Serializable(), SqlUserDefinedTypeAttribute(Format.Native, _
IsByteOrdered:=True, _
ValidationMethodName:="ValidatePoint")> _
Public Structure Point
Implements INullable
Private is_Null As Boolean
Private _x As Int32
Private _y As Int32
Public ReadOnly Property IsNull() As Boolean _
Implements INullable.IsNull
Get
Return (is_Null)
End Get
End Property
Public Shared ReadOnly Property Null() As Point
Get
Dim pt As New Point
pt.is_Null = True
Return (pt)
End Get
End Property
' Use StringBuilder to provide string representation of UDT.
Public Overrides Function ToString() As String
' Since InvokeIfReceiverIsNull defaults to 'true'
' this test is unneccesary if Point is only being called
' from SQL.
If Me.IsNull Then
Return "NULL"
Else
Dim builder As StringBuilder = New StringBuilder
builder.Append(_x)
builder.Append(",")
builder.Append(_y)
Return builder.ToString
End If
End Function
<SqlMethod(OnNullCall:=False)> _
Public Shared Function Parse(ByVal s As SqlString) As Point
' With OnNullCall=False, this check is unnecessary if
' Point only being called from SQL.
If s.IsNull Then
Return Null
End If
' Parse input string here to separate out points.
Dim pt As New Point()
Dim xy() As String = s.Value.Split(",".ToCharArray())
pt.X = Int32.Parse(xy(0))
pt.Y = Int32.Parse(xy(1))
' Call ValidatePoint to enforce validation
' for string conversions.
If Not pt.ValidatePoint() Then
Throw New ArgumentException("Invalid XY coordinate values.")
End If
Return pt
End Function
' X and Y coordinates are exposed as properties.
Public Property X() As Int32
Get
Return (Me._x)
End Get
Set(ByVal Value As Int32)
Dim temp As Int32 = _x
_x = Value
If Not ValidatePoint() Then
_x = temp
Throw New ArgumentException("Invalid X coordinate value.")
End If
End Set
End Property
Public Property Y() As Int32
Get
Return (Me._y)
End Get
Set(ByVal Value As Int32)
Dim temp As Int32 = _y
_y = Value
If Not ValidatePoint() Then
_y = temp
Throw New ArgumentException("Invalid Y coordinate value.")
End If
End Set
End Property
' Validation method to enforce valid X and Y values.
Private Function ValidatePoint() As Boolean
' Allow only zero or positive integers for X and Y coordinates.
If (_x >= 0) And (_y >= 0) Then
Return True
Else
Return False
End If
End Function
' Distance from 0 to Point method.
<SqlMethod(OnNullCall:=False)> _
Public Function Distance() As Double
Return DistanceFromXY(0, 0)
End Function
' Distance from Point to the specified point method.
<SqlMethod(OnNullCall:=False)> _
Public Function DistanceFrom(ByVal pFrom As Point) As Double
Return DistanceFromXY(pFrom.X, pFrom.Y)
End Function
' Distance from Point to the specified x and y values method.
<SqlMethod(OnNullCall:=False)> _
Public Function DistanceFromXY(ByVal ix As Int32, ByVal iy As Int32) _
As Double
Return Math.Sqrt(Math.Pow(ix - _x, 2.0) + Math.Pow(iy - _y, 2.0))
End Function
End Structure