创建用户定义类型
适用于：
SQL Server
若要创建能够在 SQL Server 中安装的用户定义的类型（UDT），必须先在受支持的 .NET Framework 编程语言之一（如 Visual C# 或 Visual Basic）中创建类，该类符合创建 UDT 的规范。 然后，可以将该类编译为动态链接库 （DLL），该库可在 SQL Server 中加载。 还可以使用 Visual Studio 创建和部署 UDT。
默认情况下，执行公共语言运行时 （CLR） 代码的功能在 SQL Server 中设置为 OFF。 可以使用 sp_configure 系统存储过程启用 CLR，如以下 Transact-SQL 语句所示：
sp_configure 'clr enabled', 1
Reconfigure
本节内容
用户定义类型要求
说明编写用户定义类型代码的要求。
用户定义类型编码
演示在创建用户定义类型的过程中涉及的编码方法。
示例
以下代码列表定义了点 UDT，该点在编码用户定义类型中进行了详细说明。
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 unnecessary 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 unnecessary 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