Monday, December 14, 2020

Upcoming Virtual Tech Events

Virtual User Group Meetings

 

Virtual Conferences

 

 

Wednesday, October 28, 2020

Separating Combo Boxes with Similar Data

A situation came up where a Windows Forms application required 2 combo boxes filled with customer IDs.  A caption of that form is shown below, where a user must select “From Customer ID” and “To Customer ID”.  Since both combo boxes were populated from the same data column, the natural thing to do was to use the same code for filling both with the same data.  However, this caused an undesirable effect.  When the user selected the “From Customer ID”, the “To Customer ID” was automatically populated with the same value. 

 

To resolve this problem, 2 separate DataTable objects must be used, dtFrom and dtTo.  Although both objects are populated using the same method (dm.GetCustomerIDNames()), keeping the objects separate will prevent one control selection from effecting the other control.  See sample code shown below.

 

 

 

        private void FillCustomerIDs()

        {

            Cursor.Current = Cursors.WaitCursor;  //Produces a "wait cursor" while data is loading

 

            //Must have 2 separate instances for the data method. 

            //DataTables must also be kept separate to prevent issues with binding

            //Data must NOT be cached, must be retrieved directly from the DB for each call. 

            //Otherwise all comboboxes will bind to the same datasource and to each other.

 

            DataTable dtFrom = dm.GetCustomerIDNames();

            FillFromCustomer(dtFrom);

 

            DataTable dtTo = dm.GetCustomerIDNames();

            FillToCustomer(dtTo);

        }

 

 

        private void FillFromCustomer(DataTable dtFrom)

        {

            AutoCompleteStringCollection acsFrom = new AutoCompleteStringCollection();

 

            foreach (var rec in dtFrom.AsEnumerable())

                acsFrom.Add(rec.ItemArray[0].ToString());

 

            cbFromCustomerID.AutoCompleteCustomSource = acsFrom;

            cbFromCustomerID.AutoCompleteMode = AutoCompleteMode.SuggestAppend;

            cbFromCustomerID.AutoCompleteSource = AutoCompleteSource.CustomSource;

 

            cbFromCustomerID.DataSource = dtFrom;

            cbFromCustomerID.DisplayMember = "ID";

            cbFromCustomerID.ValueMember = "Name";

            cbFromCustomerID.SelectedIndex = -1;    //Forces a blank item in the comboBox

        }

 

 

        private void FillToCustomer(DataTable dtTo)

        {

            AutoCompleteStringCollection acsTo = new AutoCompleteStringCollection();

 

            foreach (var rec in dtTo.AsEnumerable())

                acsTo.Add(rec.ItemArray[0].ToString());

 

            cbToCustomerID.AutoCompleteCustomSource = acsTo;

            cbToCustomerID.AutoCompleteMode = AutoCompleteMode.SuggestAppend;

            cbToCustomerID.AutoCompleteSource = AutoCompleteSource.CustomSource;

 

            cbToCustomerID.DataSource = dtTo;

            cbToCustomerID.DisplayMember = "ID";

            cbToCustomerID.ValueMember = "Name";

            cbToCustomerID.SelectedIndex = -1;

        }

 

 

Thursday, September 24, 2020

Sep/Oct'20 Events

Virtual User Group Meetings

Sep 29: .Net Virtual User Group - “VS/Code Hidden Gems”

https://www.meetup.com/dotnet-virtual-user-group/events/

Oct 15: Akron AITP User Group – “Enterprise Architecture in the Cloud”

https://www.meetup.com/AkronAITP/events/

Oct 21: Hudson Software Craftsmanship - “Crafting Better Software”

https://www.meetup.com/Hudson-Software-Craftsmanship-Meetup/

Oct 22: Cleveland C#/VB.Net User Group - “Multi-Model Databases in Azure SQL”

https://www.meetup.com/Cleveland-C-VB-Net-User-Group/

 

Virtual Conferences

Sep 26: Northern Virginia Code Camp

https://novacodecamp.org/index.html

Oct 3: SQL Saturday-Memphis

https://www.sqlsaturday.com/1003/

Oct 24: SQL Saturday-Oregon

https://www.sqlsaturday.com/1000/

 

Sorting and Filtering ADO Objects

Listed below is an example of using Sorting and Filtering on ADO objects.  This examples utilizes an Oracle DB, but ADO objects can be used with various databases.  In this situation, the entire data table is retrieved in memory.  When needed, that data table can be sorted using a specific column or filtered using the SELECT method with the specified predicate.

 

        public void ProcesssData()

        {

//Retrieve entire data table into memory

gPOLines = RGNdm.GetLineNumsByPO(PO);


 //Create a VIEW from the in-memory data table

var newView = gPOLines.DefaultView.ToTable(false, "PART_ID", "PO_NUMBER", "CREATE_DATE", "VENDOR_NAME", "INITIATED_BY");


//SORT by desired field

gPOLines.DefaultView.Sort = " PART_ID ASC ";

 

//SELECT (filter) for specific criteria

                DataRow[] filteredRows = gPOLines.Select($" PART_ID = '{cbPartID1.Text}' ");

 

                if (filteredRows.Count() >= 1)

                {

                    decimal userOrderQty = (decimal)filteredRows[0].Field<double>("USER_ORDER_QTY");

                }

        }

 

        public DataTable GetLineNumsByPO(string PO)

        {

            string sql = $" SELECT LINE_NO, PART_ID, USER_ORDER_QTY FROM PO_TABLE ";

            OracleDataAdapter da = new OracleDataAdapter(sql, User.connString);

            DataTable tbl = new DataTable();

            da.Fill(tbl);

            return tbl;

        }

 

Wednesday, September 23, 2020

Capturing the file name and line number of an Exception

Handling exceptions is a critical task in any application.  When an exception is logged, it needs to have sufficient detail so it can be researched at a later time.  In addition, as a developer, you want to extract and log as much detail about it as possible.  Some of those details include the file name and line number where the exception occurred.  Listed below is a method that handles exceptions, extracts the message, file name, and line number for logging.

 

 

        private void ProcessEx(Exception ex, string details = "")

        {

            int lineNumber = 0;

            const string lineNumberMarker = ":line ";

            string traceText = ex.StackTrace + "";  //Adding empty space will ensure final value is never null

 

            int lineIndex = traceText.LastIndexOf(lineNumberMarker);

            if (lineIndex >= 0)

            {

                string lineNumberText = traceText.Substring(lineIndex + lineNumberMarker.Length);

                int.TryParse(lineNumberText, out lineNumber);

            }

 

            string fileName = string.Empty;

            const string fileNameMarker = " in ";

            int fileNameIndex = traceText.LastIndexOf(fileNameMarker);

            if (fileNameIndex >= 0)

            {

                int fileNameStart = fileNameIndex + fileNameMarker.Length;

                int fileNameLength = lineIndex - fileNameIndex - fileNameMarker.Length;

                fileName = traceText.Substring(fileNameStart, fileNameLength);

            }

 

            //Log error message + file/line info

            string msg = $"Error: {ex.Message}. \r\n{details}";

            string fileInfo = $"\r\nFile {fileName}, Line {lineNumber} ";

            Logging lg = new Logging();

            lg.WriteLog(msg + fileInfo);           

        }

 

Friday, September 18, 2020

Changing DB Password in Oracle SQL Developer

While working with Oracle SQL Developer, you may encounter the following message when the password is near expiration.

 

5

 

A database warning was encountered performing the requested operation:

 

ORA-28002: the password will expire within 5 days

28002. 00000 -  "the password will expire within %s days"

*Cause:    The user's account is about to expire and the password

           needs to be changed

*Action:   change the password or contact the DBA

Vendor code 28002

 

 

To change the password:

  1. Open the Connections tab (View > Connections)
  2. Right click the database where the password needs to be changed
  3. Select “Reset Password…”

 

 

  1. A pop-up form (see below) will appear prompting for the old and new passwords.

 

 

That’s it.  Seems simple but if you’re not familiar with SQL Developer, this can be a frustrating.

Wednesday, September 2, 2020

Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

Overview: I have a Windows Form application, built in .Net 4.7.2 using Visual Studio 2019.  The form has 3 PartID combo boxes, allowing the user to select 3 distinct part IDs from a finite list of parts in the drop down.

 

 

Problem: When the combo box was being filled with values in the drop down list, the following exception was thrown.

 

Exception:

System.AccessViolationException

  HResult=0x80004003

  Message=Attempted to read or write protected memory. This is often an indication that other memory is corrupt.

  Source=<Cannot evaluate the exception source>

  StackTrace:

<Cannot evaluate the exception stack trace>

 

Code:

        private void cbPO_LostFocus(object sender, EventArgs e)

        {

            FillPartID1(poLines);

        }

 

 

        private void cbPO_SelectedIndexChanged(object sender, EventArgs e)

        {

            FillPartID1(poLines);

        }

 

        private void FillPartID1(DataTable poLines)

        {

            AutoCompleteStringCollection acs1 = new AutoCompleteStringCollection();

 

            foreach (var rec in poLines.AsEnumerable())

               acs1.Add(rec.ItemArray[1].ToString());           

 

            cbPartID1.AutoCompleteCustomSource = acs1;

            cbPartID1.AutoCompleteMode = AutoCompleteMode.SuggestAppend;    //Exception thrown here during 2nd execution

            cbPartID1.AutoCompleteSource = AutoCompleteSource.CustomSource;

 

            cbPartID1.DataSource = poLines;

            cbPartID1.DisplayMember = "PART_ID";

            cbPartID1.ValueMember = "PART_ID";

            cbPartID1.SelectedIndex = -1;

        }

 

Cause: The FillPartID1() was being called twice due to event handlers cbPO_SelectedIndexChanged() and cbPO_LostFocus().

 

Solution: Refactor the code so FillPartID1() is called only once.

ComboBox selection changes selection in other comboBox controls

Overview: I have a Windows Form application, built in .Net 4.7.2 using Visual Studio 2019.  The form has 3 PartID combo boxes, allowing the user to select 3 distinct part IDs from a finite list of parts in the drop down.

 

 

Problem: Once the user selects a PartID in any combo box, the other 2 combo boxes are automatically set to that value.

 

 

        private void Start()

        {

            DataTable POLines = GetLineNumsByPO(PO);

 

            FillPartID1(POLines);

            FillPartID2(POLines);

            FillPartID3(POLines);           

        }

 

 

        private void FillPartID1(DataTable poLines)

        {

            AutoCompleteStringCollection acs1 = new AutoCompleteStringCollection();

 

            foreach (var rec in poLines.AsEnumerable())

               acs1.Add(rec.ItemArray[1].ToString());           

 

            cbPartID1.AutoCompleteCustomSource = acs1;

            cbPartID1.AutoCompleteMode = AutoCompleteMode.SuggestAppend;

            cbPartID1.AutoCompleteSource = AutoCompleteSource.CustomSource;

 

            cbPartID1.DataSource = poLines;

            cbPartID1.DisplayMember = "PART_ID";

            cbPartID1.ValueMember = "PART_ID";

            cbPartID1.SelectedIndex = -1;

        }

 

 

        private void FillPartID2(DataTable poLines)

        {

            AutoCompleteStringCollection acs2 = new AutoCompleteStringCollection();

 

            foreach (var rec in poLines.AsEnumerable())

                acs2.Add(rec.ItemArray[1].ToString());

 

            cbPartID2.AutoCompleteCustomSource = acs2;

            cbPartID2.AutoCompleteMode = AutoCompleteMode.SuggestAppend;

            cbPartID2.AutoCompleteSource = AutoCompleteSource.CustomSource;

 

            cbPartID2.DataSource = poLines;

            cbPartID2.DisplayMember = "PART_ID";

            cbPartID2.ValueMember = "PART_ID";

            cbPartID2.SelectedIndex = -1;

        }

 

 

        private void FillPartID3(DataTable poLines)

        {

            AutoCompleteStringCollection acs3 = new AutoCompleteStringCollection();

 

            foreach (var rec in poLines.AsEnumerable())

                acs3.Add(rec.ItemArray[1].ToString());

 

 

            cbPartID3.AutoCompleteCustomSource = acs3;

            cbPartID3.AutoCompleteMode = AutoCompleteMode.SuggestAppend;

            cbPartID3.AutoCompleteSource = AutoCompleteSource.CustomSource;

 

            cbPartID3.DataSource = poLines;

            cbPartID3.DisplayMember = "PART_ID";

            cbPartID3.ValueMember = "PART_ID";

            cbPartID3.SelectedIndex = -1;

        }

 

 

Solution: The Start() method was modified to have 3 separate datatables, each one passed to a partID comboBox.  This resolved one combo box selection updating the other combo boxes

 

        private void Start()

        {

            //3 separate datatables were required to avoid having one PartID selection update another PartID control.

            DataTable POLines1 = GetLineNumsByPO(PO);

            DataTable POLines2 = GetLineNumsByPO(PO);

            DataTable POLines3 = GetLineNumsByPO(PO);

 

            FillPartID1(POLines1);

            FillPartID2(POLines2);

            FillPartID3(POLines3);           

        }

 

Thursday, August 27, 2020

Sep' 20 .Net Events

Virtual User Group Meetings

Sep 1: ONSQL-Cleveland “SQL Azure Deployment Options”

https://ohionorth.pass.org/

 

Sep 10: .Net Virtual User Group “Adding a little DAPR to .NET Microservices”

https://www.meetup.com/dotnet-virtual-user-group/events/272490405/

 

Sep 16: Hudson Software Craftsmanship “Crafting Better Software”

https://www.meetup.com/Hudson-Software-Craftsmanship-Meetup/

 

Sep 24: Cleveland C#/VB.Net User Group

https://www.meetup.com/Cleveland-C-VB-Net-User-Group/

 

 

Virtual Conferences

Aug 28: .NET Dev Summit 2020 (Bengaluru): https://bdotnet.in/dotnet-dev-summit-2020/

 

Aug 29: SQL Saturday (Salt Lake City, UT): https://www.sqlsaturday.com/997/

 

Monday, August 10, 2020

.Net Virtual Events - Aug 2020

Like Technical Events?  Me too!  Here’s a list of .Net related events online and free of charge.

Aug 11: “Come meet the new .NET Standard MVVM” - https://www.meetup.com/dotnet-virtual-user-group/events/272490308

Aug 12-14: Pittsburgh Tech Fest - http://www.pghtechfest.com/

Aug 13: “Migrate Your Apps and SQL Server Databases to Azure” - https://info.microsoft.com/ww-landing-azure-webinar-series-migrate-your-apps-and-sql-server-databases-to-azure.html?lcid=en-us&ocid=mkto_eml_EM666897A1LA1&ocid=eml_pg189324_gdc_comm_az

Aug 13: “Breaking Bad Habits: Solutions for Common Query Antipatterns” - https://www.meetup.com/Louisville-Data-Technology-Group/events/270966985/

Aug 13-14: JavaScript & Friends Conference - https://www.javascriptandfriends.com/  

Aug 19: Hudson Software Craftsmanship - https://www.meetup.com/Hudson-Software-Craftsmanship-Meetup/

Aug 27: “Dialogue with your Data: Interactive AI with Cognitive Services” - https://www.meetup.com/Cleveland-C-VB-Net-User-Group/events/272490398/?isFirstPublish=true

Aug 29: SQL Saturday-Salt Lake City: https://www.sqlsaturday.com/997/eventhome.aspx

 

Sign up and skill up!

Friday, July 31, 2020

Global 2020 Summer AI/ML Fest

The Global 2020 Summer AI/ML Fest is a virtual event with 8 tracks (3 Developer, 3 Business, 2 ML).  The event took place on Friday, July 31, 2020.  If you missed this free event or want to revisit some of the sessions, the links below provide access to all content:

 

Full listing of all sessions: https://aka.ms/summer2020-globalaimlfest.com

 

Presentation Slides: https://aka.ms/downloads-global2020summeraimlfest

 

Recorded Sessions:  https://aka.ms/azurecloudevents  

 

Thursday, July 23, 2020

Monday, June 29, 2020

KeyCode vs. KeyData vs. KeyValue

When trying to examine user keystrokes in Windows Forms, the .Net Framework and .Net Core offer a variety of properties:

 

Keys: an enumeration in the System.Windows.Forms namespace that Specifies key codes and modifiers.

 

KeyCode: returns the System.Windows.Forms.Keys value that is the key code for the event.

 

KeyData: Returns the System.Windows.Forms.Keys representing the key code for the key that was pressed, combined with modifier flags that indicate which combination of CTRL, SHIFT, and ALT keys was pressed at the same time.

 

KeyValue: returns the integer representation of the KeyCode property.

 

 

Example:

tbUnitPrice.PreviewKeyDown += new PreviewKeyDownEventHandler(this.tbUnitPrice_PreviewKeyDown);  //Add event handler to capture keystroke

 

 

        private void tbUnitPrice_PreviewKeyDown(object sender, PreviewKeyDownEventArgs e)

        {

            var keycode = e.KeyCode;

            var keydata = e.KeyData;

            var keyValue = e.KeyValue;

 

            if ( (keycode == Keys.Tab) || (keycode == Keys.Enter) )

            {

                dgParts.CurrentCell = dgParts.Rows[dgParts.CurrentRow.Index + 1].Cells[0];                   //Move to the 1st cell of the next row

 

            }

        }