Sql-server – Why can’t C# SMO see extended properties on a column but Powershell SMO can

cpowershellsmosql serversql-server-2012

I am attempting to read extended properties on tables and columns in a winforms C# application. I am using SQL Server SMO to do so. When I execute the application it does not see the extended properties, but when I read the extended properties using PowerShell, it does see the extended properties.

The C# code:

var x = col.ExtendedProperties.Count;
var NPI = col.ExtendedProperties["NPI"].Value;
bool npi = bool.Parse(NPI.ToString());

The PowerShell code:

Add-Type -AssemblyName "Microsoft.SqlServer.Smo, Version=11.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91"
$server = New-Object Microsoft.SqlServer.Management.Smo.Server $env:COMPUTERNAME
$server.Databases["<db name>"].Tables["<table name>"].Columns["<column name>"].ExtendedProperties | Select Name, Value, State

I have checked and both Visual Studio and PowerShell are using the same version of SMO (11.0.0.0). When I execute the C# code the col.ExtendedProperties.Count = 0, but when I execute the PowerShell code I get:

Name Value    State
---- -----    -----
NPI  False Existing

Does anyone have any ideas as to why this could be happening?

Additional Information

In the C# code I open up a DataReader on a table using:

sourceServer.ConnectionContext.ExecuteReader(<select command>)

to retrieve the data from the table. I then go into a while loop with DataReader and inside that while loop I have:

foreach (Column col in sourceTable.Columns) 
{ 
StringBuilder cleanData = CleanseColumn(col, dr[col.Name].ToString());
sbvalues.Append("'" + cleanData + "', "); 
}

When I step through the foreach, the sourceTable variable has its extended property, but the col column variable does not.

Best Answer

I just want to shadow @BradC a little. I tested his code on Visual Studio 2015 (Update 3) on a Windows 10 Pro x64 machine against an SQL Server 2014 instance and I can confirm you can get Extended Properties of a field without issues.

To replicate I use one of my local databases. I used the following code snip to define some extended properties.

USE MyLocalDb;
GO
EXEC sys.sp_addextendedproperty 
@name = N'MS_DescriptionExample', 
@value = N'Some EP example.', 
@level0type = N'SCHEMA', @level0name = dbo, 
@level1type = N'TABLE',  @level1name = tblATableWithAtblPrefix,
@level2type = N'COLUMN', @level2name = Forename;
GO

I created a new console project and added the following references:

Microsoft.SqlServer.ConnectionInfo
Microsoft.SqlServer.Management.Sdk.Sfc
Microsoft.SqlServer.Smo
Microsoft.SqlServer.SqlEnum

All from:

\%Install Path%\Microsoft SQL Server\130\SDK\Assemblies\

So my whole code, based on @BradC's looks like:

using System;
using System.Data.SqlClient;
using Microsoft.SqlServer.Management.Smo;
using Microsoft.SqlServer.Management.Common;

namespace ConsoleApplication7
{
    class Program
    {
        private static Database database;
        static void Main(string[] args)
        {
            Microsoft.SqlServer.Management.Smo.Server server;

            SqlConnection connection = new SqlConnection("Integrated Security=SSPI; Data Source=SIS_DBA");
            Microsoft.SqlServer.Management.Common.ServerConnection serverConnection = 
                new Microsoft.SqlServer.Management.Common.ServerConnection(connection);

            server = new Server(serverConnection);

            database = server.Databases["ImmigSql"];

            foreach (Table table in database.Tables)
            {
                Console.WriteLine(" " + table.Name);
                foreach (Column col in table.Columns)
                {
                    Console.WriteLine("  " + col.Name + " " + col.DataType.Name);
                    foreach (var property in col.ExtendedProperties)
                    {
                        Console.WriteLine(" " + property.ToString() + "");
                    }
                }
            }
            Console.ReadLine();
        }
    }
}

enter image description here

Of course you can now access the properties and use their values.

The Count value that wasn't working on your example:

enter image description here

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