We Keep Coding

Is C# 7 working in VS 15 Preview 4?

I tried a simple test but it didn't like out variables
As a simple test, I wrote this (perhaps there is something simple wrong with it, but I also had trouble with patterns and with tuples)
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication2
{
public class Program
{
static void Main(string[] args)
{
Runner runner = new ConsoleApplication2.Runner();
Point p = new ConsoleApplication2.Point();
runner.PrintCoordinates(p);
}
}
public class Point
{
int x = 20;
int y = 50;
public void GetCoordinates(out int a, out int b)
{
a = x;
b = y;
}
}
public class Runner
{
public void PrintCoordinates(Point p)
{
p.GetCoordinates(out int x, out int y);
Console.WriteLine($"({x}, {y})"); // x does not exist in current context
}
}
}

According to this post, where the PrintCoordinates example method comes from:
Note: In Preview 4, the scope rules are more restrictive: Out variables are scoped to the statement they are declared in. Thus, the above example will not work until a later release.
The new tuples suffer from a similar problem, though it seems you can partially work around that with a NuGet download:
Note: Tuples rely on a set of underlying types, that aren’t included in Preview 4. To make the feature work, you can easily get them via NuGet:
Right-click the project in the Solution Explorer and select “Manage NuGet Packages…”
Select the “Browse” tab, check “Include prerelease” and select “nuget.org” as the “Package source”
Search for “System.ValueTuple” and install it.

Unable to instantiate class with constructor

I'm pretty sure this is a duplicate, but I've been unable to find a fix for this after a few hours of searching/trying.
I'm not an advanced programmer, but I have a decent amount of C++ experience. I'm trying to learn C# and having trouble with very basic syntax, especially for just accessing other classes. I've been looking for simple examples for a while, and overwhelmingly, everything I find seems to use one HUGE class, wherein the main method is used, so those examples haven't been very helpful.
I want to develop a solution with multiple .cs files (one class in each), and another .cs file containing the main method that I'll use for testing. My solution is named DIVAT. I have a Dealer.cs file with the following code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace DIVAT
{
public class Dealer
{
public List<Tuple<int, string>> deck;
Dealer()
{ // default constructor
Console.Out.WriteLine("Default constructor called. (Dealer class)");
string [] suitValue = {"c", "d", "h", "s"};
for(int i = 2; i <= 14; i++){
for(int j = 0; j <= 3; j++){
deck.Add(new Tuple<int, string>(i, suitValue[j]));
}
}
}
~Dealer()
{// destructor
Console.Out.WriteLine("Destrcutor called. (Dealer class)");
}
Tuple<int, string> Dealer.getCard(int cardNum)
{// getter
return deck[cardNum];
}
}
}
Now I'm just trying to test this in another file, Program.cs. I'm hitting 2 bugs and can't figure out why. I am having a lot of trouble just trying to initialize my Dealer class. Also, I just want to test a getter function in my Dealer class.
I use to have a lot more static and private keywords throughout, but took those out as I was hitting bugs.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace DIVAT
{
class Program
{
static void Main(string[] args)
{
Dealer dealer = new Dealer();
// inaccessible due to it's protection level...
for (int i = 0; i <= 52; i++) {
Console.Out.WriteLine(dealer.getCard(i));
// does not contain a definition for getCard...
}
}
}
}
Sorry for such the basic questions, but I've been scouring the internet and trying different ways to fix this and have been unsuccessful. I feel like once I get past these few bugs, I should be able to convert a lot of my other code relatively painlessly.

Your constructor is implicitly private and since you provide zero public constructors, it cannot instantiate your class, even though the class itself is public..
You need to specify that it is public.
public Dealer() { }
As for your second question, you don't need to tell your methods that they belong to the class. They are already aware. Change your method signature like so:
public Tuple<int, string> GetCard(int cardNum)
{
// getter
return deck[cardNum];
}
Note that now the method is public and that we are scoped properly. In addition, note the PascalCasing on your method name. This is the appropriate naming convention for method names in C#.
Also, on another note, since C# is a managed language, you probably don't need your destructor.

System.Text.RegularExpressions.Regex.Replace error in C# for SSIS

I am using the below code to write a ssis package in C# and when I write this code i get an error
using System;
using System.Data;
using Microsoft.SqlServer.Dts.Pipeline.Wrapper;
using Microsoft.SqlServer.Dts.Runtime.Wrapper;
using System.Text.RegularExpressions;
[Microsoft.SqlServer.Dts.Pipeline.SSISScriptComponentEntryPointAttribute]
public class ScriptMain : UserComponent
{
public override void PreExecute()
{
base.PreExecute();
}
public override void PostExecute()
{
base.PostExecute();
}
string toreplace = "[~!##$%^&*()_+`{};':,./<>?]";
string replacewith = "";
public override void Input0_ProcessInputRow(Input0Buffer Row)
{
Regex reg = new Regex(toreplace);
Row.NaN = reg.Replace(Row.Na, replacewith);
}
}
The error is
The best overloaded method match for
'System.Text.RegularExpressions.Regex.Replace(string,System.Text.RegularExpressions.MatchEvaluator)' has some invalid arguments
Here Na is the input column and NaN is the output column both are varchar with special characters in Inpout column.
Exceptions:
System.ArgumentNullException
System.ArgumentOutofRangeException
This is the code in the BufferWrapper in the SSIS package
/* THIS IS AUTO-GENERATED CODE THAT WILL BE OVERWRITTEN! DO NOT EDIT!
* Microsoft SQL Server Integration Services buffer wrappers
* This module defines classes for accessing data flow buffers
* THIS IS AUTO-GENERATED CODE THAT WILL BE OVERWRITTEN! DO NOT EDIT! */
using System;
using System.Data;
using Microsoft.SqlServer.Dts.Pipeline;
using Microsoft.SqlServer.Dts.Pipeline.Wrapper;
public class Input0Buffer: ScriptBuffer
{
public Input0Buffer(PipelineBuffer Buffer, int[] BufferColumnIndexes, OutputNameMap OutputMap)
: base(Buffer, BufferColumnIndexes, OutputMap)
{
}
public BlobColumn Na
{
get
{
return (BlobColumn)Buffer[BufferColumnIndexes[0]];
}
}
public bool Na_IsNull
{
get
{
return IsNull(0);
}
}
public Int32 NaN
{
set
{
this[1] = value;
}
}
public bool NaN_IsNull
{
set
{
if (value)
{
SetNull(1);
}
else
{
throw new InvalidOperationException("IsNull property cannot be set to False. Assign a value to the column instead.");
}
}
}
new public bool NextRow()
{
return base.NextRow();
}
new public bool EndOfRowset()
{
return base.EndOfRowset();
}
}
Data flow
Script component, input columns
Script component, actual script

Your code is mostly fine. You are not testing for the possibility that the Na column is NULL. Perhaps your source data doesn't allow for nulls and thus, no need to test.
You can improve your performance by scoping the Regex at the member level and instantiate it in your PreExecute method but that's just a performance thing. Has no bearing on the error message you are receiving.
You can see my package and the expected results. I sent 4 rows down, one with a NULL value, one that shouldn't change and two that have changes required.
My data Flow
I have updated my data flow to match the steps you are using in your chameleon question.
My Source Query
I generate 2 columns of data and 4 rows worth. The Na column, which matches your original question is of type varchar. The column Agency_Names is cast as the deprecated Text data type to match your subsequent updates.
SELECT
D.Na
, CAST(D.Na AS text) AS Agency_Names
FROM
(
SELECT 'Hello world' AS Na
UNION ALL SELECT 'man~ana'
UNION ALL SELECT 'p#$$word!'
UNION ALL SELECT NULL
) D (Na);
Data Conversion
I have added a Data Conversion Transformation after my OLE DB Source. Reflecting what you have done, I converted my Agency_Name to a data type of string [DT_STR] with a length of 50 and aliased it as "Copy of Agency_Name".
Metadata
At this point, I verify that the metadata for my data flow is of type DT_STR or DT_WSTR which are the only allowable inputs for the upcoming call to the regular expression. I confirm that Copy of Agency_Names is the expected data type.
Script Task
I assigned ReadOnly usage to the columns Na and Copy of Agency_Name and aliased the later as "AgencyNames".
I added 2 output columns: NaN which matches your original question and created AgencyNamesCleaned. These are both configured to be DT_STR, codepage 1252, length of 50.
This is the script I used.
public class ScriptMain : UserComponent
{
string toreplace = "[~!##$%^&*()_+`{};':,./<>?]";
string replacewith = "";
public override void Input0_ProcessInputRow(Input0Buffer Row)
{
Regex reg = new Regex(toreplace);
// Test for nulls otherwise Replace will blow up
if (!Row.Na_IsNull)
{
Row.NaN = reg.Replace(Row.Na, replacewith);
}
else
{
Row.NaN_IsNull = true;
}
if (!Row.AgencyNames_IsNull)
{
Row.AgencyNamesCleaned = reg.Replace(Row.AgencyNames, replacewith);
}
else
{
Row.AgencyNamesCleaned_IsNull = true;
}
}
}
Root cause analysis
I think your core issue may be is that the Na column you have isn't a string compatible type. Sriram's comment is spot on. If I look at the autogenerated code for the column Na, in my example I see
public String Na
{
get
{
return Buffer.GetString(BufferColumnIndexes[0]);
}
}
public bool Na_IsNull
{
get
{
return IsNull(0);
}
}
Your source system has provided metadata such that SSIS thinks this column is binary data. Perhaps it's NTEXT/TEXT or n/varchar(max) in the host. You need to do something to make it a compatible operand for the regular expression. I would clean up the column type in the source but if that's not an option, use a Data Conversion transformation to make it into a DT_STR/DT_WSTR type.
Denouement
You can observe in the Data Viewer, attached to my first image, that NaN and AgencyNamesCleaned have correctly stripped the offending characters. Furthermore, you can observe that my Script Task does not have a red X attached to it as your does. This indicates the script is in an invalid state.
As you had created the "Copy of Agency_Names" column from the Data Conversion Component as DT_TEXT, wired it up to the Script Component, and then changed the data type in the Data Conversion Component, the Red X on your script might be resolved by having the transformation refresh its metadata. Open the script and click recompile (ctrl-shift-b) for good measure.
There should be no underlines in your reg.Replace(... code. If there is, there is another facet to your problem that has not been communicated. My best advice at that point would be to recreate a proof of concept package, exactly as I have described and if that works, it becomes an exercise in finding the difference between what you have working and what you do not have working.

LINQ to Entities - Best way to accomplish this?

OK, I am mostly a LAMP developer so I am new to the entity framework. However, I am familiar with the basics in LINQ and have generated a entity model from my DB. Now here is my requirement:
I have a datagrid on a WinForm that will be refreshed from a data source on a remote server every few seconds as changes to the dataset are made from other sources. Obviously, I'd like to construct a lambda expression to get the right anonymous type to satisfy the columns that needs to be shown in my datagrid. I have done this and here is the result (I'm using a custom datagrid control, btw):
And my code thus far:
Models.dataEntities objDB = new Models.dataEntities();
var vans = from v in objDB.vans
select v;
gcVans.DataSource = vans;
OK, so now I have my basic data set. One problem I had is that the "Status" column will show a calculated string based on several parameters in the data set. I added this to my entities via a partial class. As you can see in the screenshot, this is working correctly:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace WindowsFormsApplication1.Models {
public partial class van {
public string van_status {
get {
if (this.is_offline == 1) {
return "Offline";
} else if (this.is_prayer_room == 1) {
return "In Prayer Room";
} else {
return "TODO: Create statuses";
}
}
}
}
}
This added property works fine. However, the second I try to project the status in an anonymous type so I can also retrieve the school name, I get an error:
Models.dataEntities objDB = new Models.dataEntities();
var vans = from v in objDB.vans
select new {
van_name = v.van_name,
school_name = v.school.school_name,
capacity = v.capacity,
phone = v.phone,
van_status = v.van_status
};
gcVans.DataSource = vans;
So, I have two questions:
1) If I cannot use computed properties of my partial classes in LINQ projections, how am I supposed to show my computed string in my datagrid?
2) Am I even approaching this correctly? When I resolve #1, how would I refresh this data (ie during a timer fire event)? Would I simply call objDB.refresh() and then tell my datagrid to update from the datasource? Does calling that method actually run the lambda expression above or does it load everything from the DB?
Thanks for any assistance with this. Also, if you have any best practices to share that would be awesome! I hope I explained this as thoroughly as you need to provide assistance.

1) Instead of modifying your EF object with a partial class you could always create your own class that contains your read only property van_status. The code you've got would be nearly identical:
Models.dataEntities objDB = new Models.dataEntities();
gcVans.DataSource = from v in objDB.vans
select new DisplayVan {
van_name = v.van_name,
school_name = v.school.school_name,
capacity = v.capacity,
phone = v.phone,
};
The van_status property, since it's read-only, will not need to be specified in the query.
2) I'm more a web developer than a desktop developer so I'll give you my take on how to refresh the grid (it may not be the preferred methodology for fat clients)...
I'm reluctant to trust .Refresh() methods and hope all works to maximal efficiency and work properly. Instead, encapsulate the code from #1 in a method of your own and invoke it from your timer event firing (or however you choose to implement the periodic refresh).

Another good option would be to create an extension method.
Here is a simple example:
using System;
namespace WindowsFormsApplication1 {
static class Program {
[STAThread]
static void Main() {
Van van = new Van();
string status = van.GetStatus();
}
}
public static class VanExtension {
public static string GetStatus(this Van van) {
if(van.is_offline == 1) {
return "Offline";
}
else if(van.is_prayer_room == 1) {
return "In Prayer Room";
}
return "TODO: Create statuses";
}
}
public class Van {
public int is_offline { get; set; }
public int is_prayer_room { get; set; }
}
}
Be sure to put this extension class in the same namespace as the entity class.

#define - Migrating C++ to C# or VB.Net

I need some advice on how to do the following in either C# and VB.net.
In C++, in my header file I do the following:
#define StartButtonPressed Input[0]==1 // Input is an array declared in .cpp file
In my .cpp file, i have a code something like this:
if(StartButtonPressed)
// do something
The reason of me doing so is so that my code is easier to read.
I tried the same thing in C# but it got error. How could I do the same thing in C# and VB.Net?
Please advice. Thanks.

There is no good reason to use a macro for this in C++; you could just as easily make it a function and the code would be far cleaner:
bool IsStartButtonPressed()
{
return Input[0] == 1;
}
Input should also probably be passed as an argument to the function, but it's hard to tell exactly where that is coming from.

You're best off creating a property in your class
protected bool StartButtonPressed {
get { return Input[0] == 1; }
}
then your code can be as before
.
.
.
if(StartButtonPressed) {
.
.
.
}
However for consistency with the .net framework I'd suggest calling the property IsStartButtonPressed
If you need to to be evaluated at the point of the if statement then you really need a function or a property. However is this is one time evaluation you can use a field
bool isStartButtonPressed = Input[0] ==1;
If you want may classes to have this functionality then I'd recommend a static function from another class, something like
public static class ButtonChecker {
public static bool IsPressed(int[] input) {
return input[0] == 1;
}
}
Then you call it anywhere with
if(ButtonChecker.IsPressed(Input)) {
.
.
}
But ultimately you cannot use macro's like you're used in C/C++. You shouldn't be worried about performance of properties and functions like this as the CLR jit compiler implementation is very very good for them
Here is an example program:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Diagnostics;
namespace ConsoleApplication1 {
public static class ButtonChecker {
public static bool IsPressed(int[] input) {
return input[0] == 1;
}
}
static class Program {
public static void Main(){
int[] Input = new int[6] { 1, 0, 2, 3,4 , 1 };
for(int i = 0; i < Input.Length; ++i){
Console.WriteLine("{0} Is Pressed = {1}", i, ButtonChecker.IsPressed(Input));
}
Console.ReadKey();
}
}
}

You could use an enum
public enum buttonCode
{
startButton = 0,
stopButton = 1
// more button definitions
}
Then maybe one function
public bool IsButtonPressed(b as buttoncode)
{
return Input[b] == 1;
}
Then your calls look like:
if IsButtonPressed(buttonCode.StartButton) { }
The only changes needed to switch button codes are then in the enum, not spread across multiple functions.
Edited to Add:
If you want individually named functions, you could do this:
public bool IsStartButtonPressed()
{
return Input[buttonCode.StartButton] == 1;
}
Still, all of the edits would be in the enum, not the functions.

Bjarne Stroustrup wrote:
The first rule about macros is: Do not use them if you do not have to. Almost every macro demonstrates a flaw in the programming language, in the program, or in the programmer.
It's worth noting two things here before saying anything else. The first is that "macro" can mean a very different thing in some other languages; one would not make the same statement about Lisp. the second is that Stroustrup is willing to take his share of the blame in saying that one reason for using macros is "a flaw in the programming language", so it's not like he's just being superior in condemning their use.
This case though isn't a flaw in the programming language, except that the language lets you do it in the first place (but has to, to allow other macros). The only purpose of this macro is to make the code harder to read. Just get rid of it. Replace it with some actual C# code like:
private bool StartButtonPressed
{
get
{
return Input[0]==1
}
}
Edit:
Seeing the comment above about wanting to be faster to code, I would do something like:
private enum Buttons
{
Start = 0,
Stop = 1,
Pause = 2,
/* ... */
}
private bool IsPressed(Buttons button)
{
return Input[(int)button] == 1;
}
And then call e.g. IsPressed(Buttons.Start). Then I'd fix the C++ to use the same approach too (in C++ I would even be able to leave out the Buttons. where I wanting particularly great concision).