Table creation in SQl

string connectionString = ConfigurationManager.ConnectionStrings["TestConnectionString"].ConnectionString;
SqlConnection con = new SqlConnection(connectionString);
string sql = "CREATE TABLE " + txtTableName.Text.Trim() + "(" + "Id int NOT NULL IDENTITY (1,1) PRIMARY KEY," + txtColumn.Text.Trim() + " nvarchar(MAX) NULL";
foreach (Control c in this.Controls)
 {
     if (c.Name.Contains("temp") && c is TextBox)
       {
          if (!String.IsNullOrEmpty(c.Text))
           {
             sql += "," + c.Text.Trim() + " nvarchar(MAX) NULL";
             count++;
            }
       }


 }
sql += ")";
SqlCommand cmd = new SqlCommand(sql, con);
con.Open();
cmd.ExecuteNonQuery();