Re: Read Data from Access DB in ComboBox - C# Discussion Boards

Dave Kreskowiak13-Jul-13 4:53

Dave Kreskowiak

13-Jul-13 4:53

Easy enough, it you just generate a random number for Red, Green and Blue values, then feed those to Color.From(int, int, int)[^] to get a Color back from it. You should know what to do with that I think.

No, we're not writing your code for you.

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Dave Kreskowiak

NotPolitcallyCorrect13-Jul-13 5:15

NotPolitcallyCorrect

13-Jul-13 5:15

You already asked this in QA. Please do not cross post.

harold aptroot13-Jul-13 5:52

harold aptroot

13-Jul-13 5:52

Generating a random colour is easy,

Color.FromArgb(random.Next() | ~0x00FFFFFF)

~0x00FFFFFF is a trick to write unchecked((int)0xFF000000), and the bitwise OR with that value sets the Alpha component to 255 (ie, fully opaque).
It's the "most random" way to generate a colour, that is, each of the 16777216 opaque colours is generated with equal probability. Unfortunately, most of those colours look like poo.
The solution is to generate a random colour in HSV space,

Color.FromArgb(HSV2RGB(random.NextDouble(), 1, 1))  
// 1, 1 makes saturated, bright colours

static int HSV2RGB(double h, double s, double v)
{
    int h_i = (int)(h * 6);
    double f = h * 6 - h_i;
    double p = v * (1 - s);
    double q = v * (1 - f * s);
    double t = v * (1 - (1 - f) * s);
    double r, g, b;
    switch (h_i)
    {
        default:
            r = v; g = t; b = p;
            break;
        case 1:
            r = q; g = v; b = p;
            break;
        case 2:
            r = p; g = v; b = t;
            break;
        case 3:
            r = p; g = q; b = v;
            break;
        case 4:
            r = t; g = p; b = v;
            break;
        case 5:
            r = v; g = p; b = q;
            break;
    }
    return (-0x01000000 | ((int)(255 * r) << 16)) | (((int)(255 * g) << 8) | (int)(255 * b));
}

-0x01000000 is yet an other trick to write unchecked((int)0xFF000000).

When generating multiple colours, this method still sort of fails: it will produce clashing colours. To avoid that, start with a random colour and add a specific offset

double h_colour = random.NextDouble();
for (int i = 0; i < colours.Length; i++)
{
    colours[i] = Color.FromArgb(HSV2RGB(h_colour, 1, 1));
    h_colour = (h_colour + 0.618033988749895) % 1;  // that's the golden ratio
}

modified 15-Jul-13 14:28pm.

Matt T Heffron15-Jul-13 8:21

Matt T Heffron

15-Jul-13 8:21

harold aptroot wrote:
~~~0x000000FF~~ ~0x00FFFFFF is a trick to write unchecked((int)0xFF000000)

FTFY
(~0x000000FF gives 0xFFFFFF00)

harold aptroot15-Jul-13 8:29

harold aptroot

15-Jul-13 8:29

I can actually not believe I did that. WTF. It's on the level of 1+1=3.

Read Data from Access DB in ComboBox

Kevin Bewley15-Jul-13 1:07

Kevin Bewley

15-Jul-13 1:07

Sounds like homework to me but here's a couple of clues:

// Instantiate a Random number generator
Random myRandom = new Random();

// Get a random number between 0 and 100
int randomNumber = myRandom.Next(101);

Now, how could I take my randomNumber and select a colour based on that value..?

Perhaps you could do a little research into system.drawing.color?

Then I need to do something like the code below to change the background colour...
this.BackColor = System.Drawing.Color.Red;

Hamed Parvini12-Jul-13 10:13

Hamed Parvini

12-Jul-13 10:13

when I add a data Source to Combo Box but when I Run program I get an err :

'O:\C#\School\School\School\bin\Debug\bin\Debug\TabrizKarDB.mdb' is not a valid path. Make sure that the path name is spelled correctly and that you are connected to the server on which the file resides.

if U get it , there is two of this : \bin\Debug\bin\Debug\

but in Directory I have One !!!!

why i get that err ?

Re: Read Data from Access DB in ComboBox

Dave Kreskowiak12-Jul-13 15:05

Dave Kreskowiak

12-Jul-13 15:05

Because you mistyped the path somewhere??

There's no way for us to tell you what the problem is because we can't see your code, your screen, your hard drive contents, or read your mind!

You have to show us the code here, inside HTML PRE tags, for us to tell you what went wrong.

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Dave Kreskowiak

Null array in a dictionary

PozzaVecia11-Jul-13 20:42

PozzaVecia

11-Jul-13 20:42

I need to instatiate a dictionary accepting null as value, but I have a syntax problem:

Dictionary<string, double[]?> d = new Dictionary<string, double[]?>()
d.Add("a", new double[2]{100,102});
d.Add("b", null);
d.Add("v", new double[2] { 99, 101 });;

Is it possible to do it?

Richard MacCutchan11-Jul-13 21:09

Richard MacCutchan

11-Jul-13 21:09

What happens when you try?

Use the best guess

OriginalGriff11-Jul-13 21:10

11-Jul-13 21:10

You don't need the '?' at all - you need that to specify a value type that can hold a null value. Reference types automatically can (as this is the default value for a reference type variable)

All arrays are reference types, regardless of whether they are array of reference or value types. So what you need to say is:

Dictionary<string, double[]> d = new Dictionary<string, double[]>();
d.Add("a", new double[2] { 100, 102 });
d.Add("b", null);
d.Add("v", new double[2] { 99, 101 });

You would only need the '?' if you wanted an array of doubles that could hold null values, and then the syntax would be:

double?[] da = new double?[10];

To indicate that the individual elements of the array could contain nulls.

The universe is composed of electrons, neutrons, protons and......morons. (ThePhantomUpvoter)

PozzaVecia11-Jul-13 21:59

PozzaVecia

11-Jul-13 21:59

Thanks in this way I'm not able to find the Max value of first element

var ks = d.Max(v => v.Value[0]);

I didn't clarify before this port sorry

OriginalGriff11-Jul-13 22:24

11-Jul-13 22:24

Then all you need to do is change the lambda expression to allow for the null value:

var ks = d.Max(v => v.Value == null ? 0.0 : v.Value[0]);

The universe is composed of electrons, neutrons, protons and......morons. (ThePhantomUpvoter)

PozzaVecia11-Jul-13 23:45

PozzaVecia

11-Jul-13 23:45

thanks in this case I see you need a "hard coded" value 0.0. Is it possible to say "if null just skip it"?

OriginalGriff11-Jul-13 23:58

11-Jul-13 23:58

No, there is no way to "miss out" a value in a IEnumerable iteration.
You could use double.MinValue instead:

var ks = d.Max(v => v.Value == null ? double.MinValue : v.Value[0]);

var ks = d.Max(v => { if (v.Value == null) return null; return v.Value[0]; });

But then you need to check for null in the ks variable as a list with all nulls with return a null instead of a double value.

The universe is composed of electrons, neutrons, protons and......morons. (ThePhantomUpvoter)

Richard Deeming12-Jul-13 1:51

Richard Deeming

12-Jul-13 1:51

OriginalGriff wrote:
No, there is no way to "miss out" a value in a IEnumerable iteration.

Ahem![^]

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

OriginalGriff12-Jul-13 3:37

12-Jul-13 3:37

Hadn't thought of Where - good point!

The universe is composed of electrons, neutrons, protons and......morons. (ThePhantomUpvoter)

Richard Deeming12-Jul-13 1:50

Richard Deeming

12-Jul-13 1:50

You can use the Where method[^] to skip the null items:

var ks = d.Where(v => v.Value != null).Max(v => v.Value[0]);

"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer

Read Minidumps through Native Code

Jay Nardev12-Jul-13 1:11

Jay Nardev

12-Jul-13 1:11

use like this

Dictionary<string, Nullable<double>[]> d = new Dictionary<string, Nullable<double>[]>();
d.Add("a", new Nullable<double>[2] { 100, 102 });
d.Add("b", null);
d.Add("v", new Nullable<double>[2] { 99, 101 }); ;

It would help you. Smile | :)

Zach.Saunders11-Jul-13 6:02

Zach.Saunders

11-Jul-13 6:02

I am revisiting a project that I have wanted to do for a long time. I am trying to read Minidumps much like BlueScreenView just with C# code. I was pointed to using

[DllImport("dbghelp.dll", SetLastError = true)]
public static extern bool MiniDumpReadDumpStream(IntPtr BaseOfDump,
   int StreamNumber,
   ref MINIDUMP_DIRECTORY Dir,
   ref IntPtr StreamPointer,
   ref UInt32 StreamSize);

And after much digging, I found this
http://www.symbolsource.org/Public/Metadata/NuGet/Project/Microsoft.Samples.Debugging.CorApi/1.4.0.0/Release/Default/Microsoft.Samples.Debugging.Native/Microsoft.Samples.Debugging.Native/DumpReader.cs[ ]

But I am having an issue with being able to pass in a string to the DumpReader and then read the return value. It appears that I need to pass a targetaddress and the length to the ReadMemory but I am getting an exception. I am very new to the whole native code thing. I like my .Net Libraries.

From DumpReader.CS

public byte[] ReadMemory(ulong targetAddress, int length)
{
    byte[] buffer = new byte[length];
    ReadMemory(targetAddress, buffer);
    return buffer;
}

From My Code:

DumpReader dr = new DumpReader(PathToDump);
dr.ReadMemory(??, ??);

Eddy Vluggen11-Jul-13 8:32

Eddy Vluggen

11-Jul-13 8:32

There's an easier example here[^]. I've got it working using the 4.0 runtime, seems the VS-IDE doesn't read them that well for the 2.0 runtime.

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]

Zach.Saunders11-Jul-13 9:52

Zach.Saunders

11-Jul-13 9:52

I see that the link in your post describes how to create a MiniDump but what I am looking to be able to do is read them. I am not interested in reading them in VS but through code like BlueScreenView

Mycroft Holmes11-Jul-13 14:01

Mycroft Holmes

11-Jul-13 14:01

Zach.Saunders wrote:
I am not interested in reading them in VS but through code like BlueScreenView

And yet you ask the question in a C# forum!

What do you mean by code like BlueScreenView.

Never underestimate the power of human stupidity
RAH

Zach.Saunders11-Jul-13 15:33

Zach.Saunders

11-Jul-13 15:33

I would like to be able to open up the .dmp files programmatically in a C# application and read the output to a form. I am trying to literally make a program that behaves just like Nirsoft's BlueScreenView.