Nikki's Lunch

I did a lot of updates on my project and since I use Entity Framework Code First, I depend on migration commands. This time, my Visual Studio suddenly does not recognize the commands. I have the following error message when attempting to enable migration: The term 'Enable-Migrations' is not recognized as the name of a cmdlet, function, script file, or operable program Some people say to reinstall entity framework with the following command: Install-Package EntityFramework -IncludePrerelease But it didn't work for me since I have it installed, so I find a way to force reinstall the package which works! The command as follow: Update-Package -reinstall EntityFramework -IncludePrerelease

Another interesting programming problem. I have the following code in VB.Net which throws error: dataRow.Delete() 'One of the rows in dataSet dataSet.Tables("TableName").Rows.Cast(Of DataRow).FirstOrDefault(Function(dr) dr("ColumnName") = certainCondition) The error says "Deleted row information cannot be accessed through the row". Pretty clear message, so I did the following: dataSet.Tables("TableName").Rows.Cast(Of DataRow).FirstOrDefault(Function(dr) dr("ColumnName") = certainCondition AndAlso dr.RowState <> DataRowState.Deleted) But the code above throws the same error. Apparently the deleted check has to be the first condition which again makes sense. Thus, the following code runs perfectly fine: dataSet.Tables("TableName").Rows.Cast(Of DataRow).FirstOrDefault(Function(dr) dr.RowState <> DataRowState.Deleted AndAlso dr("ColumnName") = certainCondition) There you go.

I encountered an interesting thing recently in my programming experience. I have the following method: Private Sub SomeMethod(parameter As Nullable(Of Double)) If parameter.HasValue Then 'Do something Else 'Do something else End If End Sub To call it, I use the following: SomeMethod(If(someObject.IsTrue, Nothing, someDouble)) However, it didn't work as I expect it to be. The one that confused me is, the HasValue always returns true although Nothing is being passed to the method.  It took me awhile to realize that the If operator in this case will return the same type for both results (true and if false). And in VB.Net, Nothing equals default value which for Double is 0.0 while I want Nothing to act as Null. Thus to fix the issue, I have to rewrite it as: If someObject.IsTrue Then SomeMethod(Nothing) Else SomeMethod(someDouble) End If