Verifique se o SQL Server (qualquer versão) está instalado?

using System.Data;
using System.Data.Sql;
using System;

...

SqlDataSourceEnumerator sqldatasourceenumerator1 = SqlDataSourceEnumerator.Instance;
DataTable datatable1 = sqldatasourceenumerator1.GetDataSources();
foreach (DataRow row in datatable1.Rows)
{
    Console.WriteLine("****************************************");
    Console.WriteLine("Server Name:"+row["ServerName"]);
    Console.WriteLine("Instance Name:"+row["InstanceName"]);
    Console.WriteLine("Is Clustered:"+row["IsClustered"]);
    Console.WriteLine("Version:"+row["Version"]);
    Console.WriteLine("****************************************");
}