Creating a User-Defined Type

Creating a User-Defined Type

 

Applies To: SQL Server 2016 Preview

To create a user-defined type (UDT) capable of being installed in SQL Server, you must first create a class in one of the supported .NET Framework programming languages, such as Visual C# or 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. You can also create and deploy UDTs using Visual Studio.

The ability to execute common language runtime (CLR) code is set to OFF by default in SQL Server. 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  

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 SQL Server Database Engine 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  

CLR User-Defined Types

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