Problem Dropping Database C#

Hi,

i have a problem dropping a database?

I have a WinForm and i can create DB, create the Tables and drop the DB via buttons.

When i start myProgram it's no problem to drop the Database.
Then i can create the database without problems.
The tables also without problems.

Now if i try to drop my whole DB, i get the error message:

SqlException Handle :System.Data.SqlClient.SqlException: Cannot drop database "XtmsDb" because it is currently in use.


The code for dropping db:

public void deleteProjectDB()
{
conn.ConnectionString = "Data Source=TURM21;Initial Catalog=master;Integrated Security=SSPI;";

sqlStr = "Drop database XTmsDB";

try
{
System.Console.WriteLine("Opening Connection...");
conn.Open();
System.Console.WriteLine("Connection opened!!!");

SqlCommand cmd = new SqlCommand(sqlStr, conn);
cmd.ExecuteNonQuery();
System.Console.WriteLine("Database dropped!!!");
}
catch (SqlException dropEx)
{
System.Console.WriteLine("SqlException Handle :{0}", dropEx.ToString());
}
finally
{
conn.Close();
System.Console.WriteLine("Connection closed!!!");
}
}


The code for creating db:

public void createProjectDB()
{
conn.ConnectionString = "Data Source=TURM21;Initial Catalog=master;Integrated Security=SSPI;";
sqlStr = projectDBStrings.getDBCreateString();

try
{
System.Console.WriteLine("Opening Connection...");
conn.Open();
System.Console.WriteLine("Connection opened!!!");
SqlCommand cmd = new SqlCommand(sqlStr, conn);
cmd.ExecuteNonQuery();
System.Console.WriteLine("Database created!!!");

}
catch (Exception)
{
System.Console.WriteLine("Could not establish Connection!");
}
finally
{
conn.Close();
System.Console.WriteLine("Connection closed!!!");
}
}

The code for creating Tables:

public void createProjectTables()
{
conn.ConnectionString = "Data Source=TURM21;Initial Catalog=XtmsDb;Integrated Security=SSPI;";
ArrayList createList = projectDBStrings.fillProjectSchema();
SqlTransaction tx;
SqlCommand cmd = new SqlCommand("", conn);
IEnumerator createListEnum = createList.GetEnumerator();

try
{
System.Console.WriteLine("Opening Connection...");
conn.Open();
System.Console.WriteLine("Connection opened!!!");
try
{
while (createListEnum.MoveNext())
{
sqlStr = (String)createListEnum.Current.ToString();
tx = conn.BeginTransaction();

cmd.CommandText = sqlStr;
cmd.Transaction = tx;
cmd.ExecuteNonQuery();

tx.Commit();

}
System.Console.WriteLine("Schema created!!!");

}
catch (SqlException deleteEx)
{
System.Console.WriteLine("SqlException Handle :{0}", deleteEx.ToString());
}
}
catch (SqlException connectionEx)
{
System.Console.WriteLine("SqlConnection Handle : {0}", connectionEx.ToString());
}
finally
{
conn.Close();

System.Console.WriteLine("Connection closed!!!");
}
}



Who can help me?