The second optional parameter of the GetSchema method is the restrictions that are used to limit the amount of schema information returned, and it is passed to the GetSchema method as an array of strings. The position in the array determines the values that you can pass, and this is equivalent to the restriction number.
For example, the following table describes the restrictions supported by the "Tables" schema collection using the Microsoft SqlClient Data Provider for SQL Server. Additional restrictions for SQL Server schema collections are listed at the end of this topic.
Restriction Name
Parameter Name
Restriction Default
Restriction Number
Catalog
@Catalog
TABLE_CATALOG
1
Owner
@Owner
TABLE_SCHEMA
2
Table
@Name
TABLE_NAME
3
TableType
@TableType
TABLE_TYPE
4
Specifying restriction values
To use one of the restrictions of the "Tables" schema collection, simply create an array of strings with four elements, then place a value in the element that matches the restriction number. For example, to restrict the tables returned by the GetSchema method to only those tables in the "Sales" schema, set the second element of the array to "Sales" before passing it to the GetSchema method.
Note
The restrictions collections for SqlClient have an additional ParameterName column. The restriction default column is still there for backwards compatibility, but is currently ignored. Parameterized queries rather than string replacement should be used to minimize the risk of a SQL injection attack when specifying restriction values.
The number of elements in the array must be less than or equal to the number of restrictions supported for the specified schema collection else an ArgumentException will be thrown. There can be fewer than the maximum number of restrictions. The missing restrictions are assumed to be null (unrestricted).
You can query the Microsoft SqlClient Data Provider for SQL Server to determine the list of supported restrictions by calling the GetSchema method with the name of the restrictions schema collection, which is "Restrictions". This will return a DataTable with a list of the collection names, the restriction names, the default restriction values, and the restriction numbers.
Example
The following examples demonstrate how to use the GetSchema method of the Microsoft SqlClient Data Provider for SQL Server SqlConnection class to retrieve schema information about all of the tables contained in the AdventureWorks sample database, and to restrict the information returned to only those tables in the "Sales" schema:
using System;
using System.Data;
using Microsoft.Data.SqlClient;
class Program
{
static void Main(string[] args)
{
string connectionString = "Data Source = localhost; Integrated Security = true; Initial Catalog = AdventureWorks";
using (SqlConnection connection = new SqlConnection(connectionString))
{
connection.Open();
// Specify the restrictions.
string[] restrictions = new string[4];
restrictions[1] = "Sales";
System.Data.DataTable table = connection.GetSchema("Tables", restrictions);
// Display the contents of the table.
DisplayData(table);
Console.WriteLine("Press any key to continue.");
Console.ReadKey();
}
}
private static void DisplayData(System.Data.DataTable table)
{
foreach (System.Data.DataRow row in table.Rows)
{
foreach (System.Data.DataColumn col in table.Columns)
{
Console.WriteLine("{0} = {1}", col.ColumnName, row[col]);
}
Console.WriteLine("============================");
}
}
}
SQL Server schema restrictions
The following tables list the restrictions for SQL Server schema collections.
.NET Framework 