مقالة
12/05/2014

Setting Properties

Properties are values that store descriptive information about the object. For example, Microsoft SQL Server configuration options are represented by the Configuration object's properties. Properties can be accessed either directly or indirectly by using the property collection. Accessing properties directly uses the following syntax:

objInstance.PropertyName

A property value can be modified or retrieved depending on whether the property has read/write access or read-only access. It is also necessary to set certain properties before an object can be created. For more information, see the SMO reference for the particular object.

Note

Collections of child objects appear as the property of an object. For example, the Tables collection is a property of a Server object. For more information, see Using Collections.

The properties of an object are members of the Properties collection. The Properties collection can be used to iterate through every property of an object.

Sometimes a property is not available for the following reasons:

The server version does not support the property, such as if you try to access a property that represents a new SQL Server feature on an older version of SQL Server.
The server does not provide data for the property, such as if you try to access a property that represents a SQL Server component that is not installed.

You can handle these circumstances by catching the UnknownPropertyException and the PropertyCannotBeRetrievedException SMO exceptions.

Setting Default Initialization Fields

SMO performs an optimization when retrieving objects. The optimization minimizes the number of properties loaded by automatically scaling between the following states:

Partially loaded. When an object is first referenced it has a minimum of properties available (such as Name and Schema).
Fully loaded. When any property is referenced, the remaining properties that are quick to load, are initialized and are made available.
Properties that use lots of memory. The remaining unavailable properties use lots of memory and have an Expensive property value of true (such as DataSpaceUsage). These properties are loaded only when specifically referenced.

If your application does fetch extra properties, besides the ones provided in the partially loaded state, it submits a query to retrieve these extra properties and scales up to the fully loaded state. This can cause unnecessary traffic between the client and server. More optimization can be achieved by calling the SetDefaultInitFields method. The SetDefaultInitFields method allows specification of the properties that are loaded when the object is initialized.

The SetDefaultInitFields method sets the property loading behavior for the rest of application or until it is reset. You can save the original behavior by using the GetDefaultInitFields method and restore it as required.

Examples

To use any code example that is provided, you will have to choose the programming environment, the programming template, and the programming language in which to create your application. For more information, see "How to: Create a Visual Basic SMO Project in Visual Studio .NET" or "How to: Create a Visual C# SMO Project in Visual Studio .NET" in SQL Server Books Online.

Getting and Setting a Property in Visual Basic

This code example shows how to get the Edition property of the Information object and how to set the SqlExecutionModes property of the ConnectionContext property to the ExecuteSql member of the SqlExecutionModes enumerated type.

'Connect to the local, default instance of SQL Server.
Dim srv As Server
srv = New Server
'Get a property.
Console.WriteLine(srv.Information.Version)
'Set a property.
srv.ConnectionContext.SqlExecutionModes = SqlExecutionModes.ExecuteSql

Getting and Setting a Property in Visual C#

{ 
//Connect to the local, default instance of SQL Server. 
Server srv; 
srv = new Server(); 
//Get a property. 
Console.WriteLine(srv.Information.Version); 
//Set a property. 
srv.ConnectionContext.SqlExecutionModes = SqlExecutionModes.ExecuteSql; 
}

Setting Various Properties Before an Object is Created in Visual Basic

This code example shows how to directly set the AnsiNullsStatus property of the Table object, and how to create and add columns before you create the Table object.

'Connect to the local, default instance of SQL Server.
Dim srv As Server
srv = New Server
'Create a new table in the AdventureWorks database. 
Dim db As Database
db = srv.Databases("AdventureWorks")
Dim tb As Table
'Specify the parent database, table schema and the table name in the constructor.
tb = New Table(db, "Test_Table", "HumanResources")
'Add columns because the table requires columns before it can be created. 
Dim c1 As Column
'Specify the parent table, the column name and data type in the constructor.
c1 = New Column(tb, "ID", DataType.Int)
tb.Columns.Add(c1)
c1.Nullable = False
c1.Identity = True
c1.IdentityIncrement = 1
c1.IdentitySeed = 0
Dim c2 As Column
c2 = New Column(tb, "Name", DataType.NVarChar(100))
c2.Nullable = False
tb.Columns.Add(c2)
tb.AnsiNullsStatus = True
'Create the table on the instance of SQL Server.
tb.Create()

Setting Various Properties Before an Object is Created in Visual C#

This code example shows how to directly set the AnsiNullsStatus property of the Table object, and how to create and add columns before you create the Table object.

{ 
//Connect to the local, default instance of SQL Server. 
Server srv; 
srv = new Server(); 
//Create a new table in the AdventureWorks2008R2 database. 
Database db; 
db = srv.Databases("AdventureWorks2008R2"); 
Table tb; 
//Specify the parent database, table schema, and the table name in the constructor. 
tb = new Table(db, "Test_Table", "HumanResources"); 
//Add columns because the table requires columns before it can be created. 
Column c1; 
//Specify the parent table, the column name, and data type in the constructor. 
c1 = new Column(tb, "ID", DataType.Int); 
tb.Columns.Add(c1); 
c1.Nullable = false; 
c1.Identity = true; 
c1.IdentityIncrement = 1; 
c1.IdentitySeed = 0; 
Column c2; 
c2 = new Column(tb, "Name", DataType.NVarChar(100)); 
c2.Nullable = false; 
tb.Columns.Add(c2); 
tb.AnsiNullsStatus = true; 
//Create the table on the instance of SQL Server. 
tb.Create(); 
}

Iterating Through All Properties of an Object in Visual Basic

This code example iterates through the Properties collection of the StoredProcedure object and displays them on the Visual Studio Output screen.

In the example, the Property object has been put in square parentheses because it is also a Visual Basic keyword.

'Connect to the local, default instance of SQL Server.
Dim srv As Server
srv = New Server
'Set properties on the uspGetEmployeedManagers stored procedure on the AdventureWorks database.
Dim db As Database
db = srv.Databases("AdventureWorks")
Dim sp As StoredProcedure
sp = db.StoredProcedures("uspGetEmployeeManagers")
sp.AnsiNullsStatus = False
sp.QuotedIdentifierStatus = False
'Iterate through the properties of the stored procedure and display.
'Note the Property object requires [] parentheses to distinguish it from the Visual Basic key word.
Dim p As [Property]
For Each p In sp.Properties
    Console.WriteLine(p.Name & p.Value)
Next

Iterating Through All Properties of an Object in Visual C#

This code example iterates through the Properties collection of the StoredProcedure object and displays them on the Visual Studio Output screen.

{ 
//Connect to the local, default instance of SQL Server. 
Server srv; 
srv = new Server(); 
//Set properties on the uspGetEmployeedManagers stored procedure on the AdventureWorks2008R2 database. 
Database db; 
db = srv.Databases("AdventureWorks2008R2"); 
StoredProcedure sp; 
sp = db.StoredProcedures("uspGetEmployeeManagers"); 
sp.AnsiNullsStatus = false; 
sp.QuotedIdentifierStatus = false; 
//Iterate through the properties of the stored procedure and display. 
  Property p; 
  foreach ( p in sp.Properties) { 
    Console.WriteLine(p.Name + p.Value); 
  } 
}

Setting Default Initialization Fields in Visual Basic

This code example shows how to minimize the number of object properties initialized in an SMO program. You have to include the using System.Collections.Specialized; statement to use the StringCollection object.

SQL Server Profiler can be used to compare the number statements sent to the instance of SQL Server with this optimization.

'Connect to the local, default instance of SQL Server.
Dim srv As Server
srv = New Server
'Reference the AdventureWorks database.
Dim db As Database
db = srv.Databases("AdventureWorks")
'Assign the Table object type to a System.Type object variable.
Dim tb As Table
Dim typ As Type
tb = New Table
typ = tb.GetType
'Assign the current default initialization fields for the Table object type to a 
'StringCollection object variable.
Dim sc As StringCollection
sc = srv.GetDefaultInitFields(typ)
'Set the default initialization fields for the Table object type to the CreateDate property.
srv.SetDefaultInitFields(typ, "CreateDate")
'Retrieve the Schema, Name, and CreateDate properties for every table in AdventureWorks.
'Note that the improvement in performance can be viewed in SQL Profiler.
For Each tb In db.Tables
    Console.WriteLine(tb.Schema + "." + tb.Name + " " + tb.CreateDate)
Next
'Set the default initialization fields for the Table object type back to the original settings.
srv.SetDefaultInitFields(typ, sc)

Setting Default Initialization Fields in Visual C#