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The Using statement in C#

Posted on 2016-10-24
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Last Modified: 2016-10-24
To date, I've been creating a public static class for connecting to host databases, and passing back a connection object. That entails closing the connection and disposing of all the associated objects.
I recently saw code that showed a using statement; I've really only used "using" declarations at the beginning of my code.
I see all of the examples online but none show the entire code for the class. Is there someone out there who'd like to share?
If you have any tips on implementing, I'm all ears!
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Question by:Euless_Tech
5 Comments
 
LVL 21

Assisted Solution

by:Tapan Pattanaik
Tapan Pattanaik earned 125 total points
ID: 41857643
Hi Euless,

This is the sample example.

-----------------------------------------////////////////Step 1////////////////----------------------------------------
<configuration>
  <connectionStrings>
    <add name="CharityManagement" 
    connectionString="Data Source=.;Initial Catalog=CharityManagement;Integrated Security=True"/>
  </connectionStrings>
</configuration> 

---------------------------------///////////////////Step 2/////////////////////-----------------------------------------------------

var connectionString=ConfigurationManager.ConnectionStrings["CharityManagement"].ConnectionString;

---------------------------------//////////////////Step 3////////////////--------------------------------------------
using (SqlConnection connection = new SqlConnection(connectionString)) 
{    
  int employeeID = findEmployeeID();    
  try    
  {

            connection.Open();
            SqlCommand command = new SqlCommand("UpdateEmployeeTable", connection);
            command.CommandType = CommandType.StoredProcedure;
            command.Parameters.Add(new SqlParameter("@EmployeeID", employeeID));
            command.CommandTimeout = 5;

            command.ExecuteNonQuery();    
   } 
   catch (Exception) 
   { 
      /*Handle error*/ 
   }

}

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LVL 12

Accepted Solution

by:
Dustin Saunders earned 250 total points
ID: 41857649
I always use using for my SQL connections (so much less to clean up).  Here is an example of my function I use to execute inserts/updates:

        public static void WriteSQL(string sqlQuery, DataTable parameters = null)
        {
            string cs = GetConnectionString();
            using (SqlConnection _cs = new SqlConnection(cs))
            {
                SqlCommand cmd = new SqlCommand(sqlQuery);

                PutParameters(cmd, parameters);

                cmd.CommandType = System.Data.CommandType.Text;
                cmd.Connection = _cs;
                _cs.Open();
                cmd.ExecuteNonQuery();
            }
        }

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(for reference, here is PutParameters)
        public static void PutParameters(SqlCommand cmd, DataTable parameters)
        {
            if (parameters != null)
            {
                foreach (DataRow row in parameters.Rows)
                {
                    if (row[2].ToString() == "int")
                    {
                        cmd.Parameters.Add(row[0].ToString(), SqlDbType.Int).Value = Convert.ToInt32(row[1]);
                    }
                    else if (row[2].ToString() == "varchar")
                    {
                        cmd.Parameters.Add(row[0].ToString(), SqlDbType.VarChar).Value = row[1].ToString();
                    }
                }
            }
        }

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Author Comment

by:Euless_Tech
ID: 41857674
Either one of you that responded ever nest the using statements?
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LVL 20

Assisted Solution

by:Daniel Van Der Werken
Daniel Van Der Werken earned 125 total points
ID: 41857687
The key factor for the Using statement is that the class  you're coding to implements IDisposable.

While I use this a lot, there are some cases where you wouldn't want to. For example, you might need a "handle" to the object outside of the open/close operations.

Most of the time though, you want to wrap everything you can in a using statement. Here's my example with iTextSharp. Note I've wrapped all the usings and this gives me a clean process.

                    using (Document iTextDocument = new Document(PageSize.A4, 0, 0, 0, 0))
                    {
                        using (FileStream sw = new FileStream(outputPDF, FileMode.Create))
                        {
                            using (PdfWriter pdfWriter = PdfWriter.GetInstance(iTextDocument, sw))
                            {
                                using (Bitmap bitmap = new Bitmap(inputTIFF))
                                {
                                    int pageCount = bitmap.GetFrameCount(FrameDimension.Page);
                                    iTextDocument.Open();
                                    PdfContentByte contentByte = pdfWriter.DirectContent;
                                    for (int i = 0; i < pageCount; i++)
                                    {
                                        bitmap.SelectActiveFrame(FrameDimension.Page, i);
                                        iTextSharp.text.Image itextImage = iTextSharp.text.Image.GetInstance(bitmap, System.Drawing.Imaging.ImageFormat.Bmp);
                                        itextImage.ScalePercent(72.0f / itextImage.DpiX * 100);
                                        itextImage.SetAbsolutePosition(0.0f, 0.0f);
                                        contentByte.AddImage(itextImage);
                                        iTextDocument.NewPage();
                                    }
                                }
                            }
                        }
                    }

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Author Closing Comment

by:Euless_Tech
ID: 41857730
Thanks guys. Appreciate the quick response.
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