access to main form from child fom (WinForms)

Assume ChildForm is opened from MainForm:


ChildForm form= new  ChildForm  ();
form.ShowDalog(this);


Now, to access MainForm from ChildForm (to refresh something on MainForm etc.), call this from child form:


MainForm parent = ( MainForm  )this.Owner;
// do sonething in parent form
this.Close(); // close child form



http://stackoverflow.com/questions/5443932/accessing-main-form-from-child-form

update error in dbcontext (ef)

When i tried to update an entity by using DbContext (entity framework), i got this error:

{"An object with the same key already exists in the ObjectStateManager. The ObjectStateManager cannot track multiple objects with the same key."}

The discussion in http://stackoverflow.com/questions/6033638/an-object-with-the-same-key-already-exists-in-the-objectstatemanager-the-object helped me to solve it.
I replaced the lines


//context.Sentence.Attach(temp);
// context .Entry(temp).State = System.Data.EntityState.Modified;


with the following:


Sentence old =  context.Sentence.Find(temp.ID);
context .Entry(old).CurrentValues.SetValues(temp);

reading an excel file in C#

In order to read an excel file cell by cell, the first step is adding Microsoft Excel Object Library as a reference to the project (http://www.c-sharpcorner.com/Forums/Thread/80161/). 
Afterwards, the following code should work:

// ..
using Excel = Microsoft.Office.Interop.Excel;
// ...

 private static void ReadExcelFile()
 {
            Excel.Application exApp ;
            Excel.Workbook exWorkBook ;
            Excel.Worksheet exWorkSheet ;
            Excel.Range range ;


            string str;
            int row = 0;
            int column = 0;


            String pwd =  Directory.GetCurrentDirectory();


            exApp = new Excel.Application();
            exWorkBook = exApp.Workbooks.Open("C:/filename.xls" );
            exWorkSheet = (Excel.Worksheet)exWorkBook.Worksheets.get_Item(1);


            range = exWorkSheet.UsedRange;


            for ( row  = 1;  row  <= range.Rows.Count; row++)
            {
                for ( column = 1;  column <= range.Columns.Count;  column  ++)
                {
                    // to allow nullable cells
                    if (range.Cells[rCnt, cCnt].Value2 == null) continue;
                    str = range.Cells[row,  column].Value2.ToString();
                }
            }


            exWorkBook.Close(true, null, null);
            exApp.Quit();
}


see these for more:
http://csharp.net-informations.com/excel/csharp-read-excel.htm
http://dontbreakthebuild.com/2011/01/30/excel-and-c-interop-with-net-4-how-to-read-data-from-excel/

JPA tips 2

A previous post about this topic: http://hilaltarakci.blogspot.com/2011/03/jpa-tips.html

Actually, long version of this post includes notes taken while i was reading Chapter 9- Working with Objects of book Java Persistence with Hibernate (http://www.manning.com/bauer2/). However, i could not post it because of the copyright rules..

 But at least, i can recommend to buy the book and read the whole chapter..

free data models

I am trying to model a complex questionnaire and during my googling for best practices i discovered this website: http://www.databaseanswers.org/data_models/
An excellent site full of free and well prepared data models on several topics..

free manual search engine

Discovering beneficial manuals, especially when newbie to a topic, technology etc.,  is vital.
 http://the-manuals.com/ seems to retrieve good documentation..

LINQ error: Null value for non-nullable member.

When i tried to save an object with a complex type (with a null instance of the complex type), i got the following error:

{"Null value for non-nullable member. Member: 'Sentence'."}

In this link there is an explanation for this: http://social.msdn.microsoft.com/Forums/en-US/adonetefx/thread/50d33271-c8e3-468f-82e1-7c3178cb4322/
According to the explanation, complex types are always considered as required in entity framework. My workaround is creating an instance of the complex type with new keyword in the constructor.

error during migration (update-database, codefirst)

I got the following error when i run Update-Database command in Package Manager Console of Visual Studio:


PM> update-database
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentException: The parameter is incorrect. (Exception from HRESULT: 0x80070057 (E_INVALIDARG))
   --- End of inner exception stack trace ---
   at System.RuntimeType.InvokeDispMethod(String name, BindingFlags invokeAttr, Object target, Object[] args, Boolean[] byrefModifiers, Int32 culture, String[] namedParameters)
   at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)
   at System.Management.Automation.ComMethod.InvokeMethod(PSMethod method, Object[] arguments)
Exception has been thrown by the target of an invocation.


The solution is specifying the startup project (http://stackoverflow.com/questions/9174116/entity-framework-4-3-migration-exception-when-update-database):


Update-Database –ProjectName "MyInnerProject" –Force -ConnectionString "Data Source=.;Initial Catalog=initialcatalogname;Persist Security Info=True;User ID=userid;Password=password" -ConnectionProviderName "System.Data.SqlClient" -verbose -StartupProjectName "MyStartupProject"

enum support in entity framework

Enumeration support comes with Entity Framework 5, so for prior versions we need a workaround..
I think the workaround in http://dotnetdevdude.com/Blog/2012/01/09/EntityFrameworkCodeFirstEnum.aspx is suitable.  To apply the workaround:
1.   Create two members for the field you want to use as enum type. In the below example,   SentencePart   is an enumaration which specifies parts of a sentence. SentencePartInt  holds an integer value whereas SentencePartEnum  is the member which is going to be used and processed in the code.

       

        public Nullable SentencePartInt{ get; set; }

        public Nullable< SentencePart> SentencePartEnum

        {

            get { return ( SentencePart) SentencePartInt ; }

            set {  SentencePartInt = (int)value; }

        }

       

2.   Tell the database context not  to persist the enum member.

       modelBuilder.Entity().Ignore(x => x. SentencePartEnum );

3.    Use the enum member in the code, not the integer.

pdf to word converter

When there is a time limit for composing a tutorial for something, a good pdf to word converter tool is a life saver. 14-day trial downloaded from http://www.pdftoword.com/ worked for me..
http://www.pdfonline.com/pdf-to-word-converter/ took a while to convert the pdf online and only converted the document partially because of its size..

clean code

While looking for coding best practices, i discovered this book: http://www.amazon.com/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882 . It is very easy to read with funny drawings..
The guidelines in  http://csharpguidelines.codeplex.com/ are worth sharing as well..