How do I store two dimensional array using session in ASP.NET?

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I need to store two dimensional array in Session that is in int originaly and then I need to retrieve from the Session. Is some way? I can not solve that for so long. It does not work and it says:

System.InvalidCastException: Unable to cast object of type 'System.Web.UI.WebControls.Label' to type 'System.Int32[,]'.

What I have tried:

I have tried everything but I can not figure that out.

Random rnd = new Random();
      int r = Convert.ToInt32(pocetR.Text);
      int s = Convert.ToInt32(pocetS.Text);
      int[,] MaticeA = new int[r, s];

      int[,] MaticeB = new int[r, s];

      for (int j = 0; j < s; j++)
      {
          for (int i = 0; i < r; i++)
          {
              int ko = rnd.Next(-50, 50);

              MaticeA[i, j] = ko;

              maticeA.Text = maticeA.Text + MaticeA[i ,j].ToString();
              maticeA.Text = maticeA.Text + " ";
              Session["MA"] = Session["MA"] + ' '.ToString();
          }
          maticeA.Text = maticeA.Text + "<br />";
          Session["MyArray"] = maticeA;
      }

      for (int j = 0; j < s; j++)
      {
          for (int i = 0; i < r; i++)
          {
              MaticeB[i, j] = rnd.Next(-50, 50);
              maticeB.Text = maticeB.Text + MaticeB[i, j].ToString();
              maticeB.Text = maticeB.Text + " ";
          }
          maticeB.Text = maticeB.Text + "<br />";
      }


  }

  protected void vypocitat_Click(object sender, EventArgs e)
  {

      int[,] fromSession = (int[,])Session["MyArray"];


      lblV.Text = fromSession[0, 1].ToString();




  }

Posted 22-May-20 2:04am

Petr Jaroš

Updated 22-May-20 2:20am

v4

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3 solutions

Solution 2

You could try to store it as an unidimensional array instead.

C#

readonly int R = 3;
readonly int C = 4;
int[,] bidim = new int[R, C];
int[] unidim = new int[R * C];

// bidim to unidim
for (int c = 0; c < C; ++c)
{
   for (int r = 0; r < R; ++r)
   {
      unidim[r * C + c] = bidim[r, c];
   }
}

// unidim to bidim
for (int c = 0; c < C; ++c)
{
   for (int r = 0; r < R; ++r)
   {
      bidim[r, c] = unidim[r * C + c];
   }
}

Posted 22-May-20 2:12am

phil.o

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Richard Deeming · Accepted Answer · 2020-05-22T02:15:00

If you're using "traditional" ASP.NET, you can just store the value directly in the session:

C#

int[,] values = { { 1, 2 }, { 42, 64 } };
Session["SomeUniqueKey"] = value;
int[,] otherValues = (int[,])Session["SomeUniqueKey"];

If you're using ASP.NET Core, things are slightly more complicated. You can directly store a byte array, and there are extension methods for strings and single integers. But there's nothing for arrays of other types, or more complicated objects.
Session in ASP.NET Core | Microsoft Docs[^]
ISession Interface (Microsoft.AspNetCore.Http) | Microsoft Docs[^]

The usual approach seems to be to serialize the value to JSON and store it as a string:

C#

int[,] values = { { 1, 2 }, { 42, 64 } };
Session.SetString("SomeUniqueKey", JsonConvert.SerializeObject(value));
int[,] otherValues = JsonConvert.DeserializeObject<int[,]>(Session.GetString("SomeUniqueKey"));

However, there may be more efficient ways to accomplish this.

F-ES Sitecore · Accepted Answer · 2020-05-22T02:10:00

Solution 1

C#

// Create
int[,] a = new int[2, 2];
a[0, 0] = 1;
a[0, 1] = 2;
a[1, 0] = 3;
a[1, 1] = 4;

// Store
Session["MyArray"] = a;

// Retrieve
int[,] fromSession = (int[,])Session["MyArray"];

Posted 22-May-20 2:10am

F-ES Sitecore

Comments

Petr Jaroš 22-May-20 8:17am

It does not work it says: System.InvalidCastException: Unable to cast object of type 'System.Web.UI.WebControls.Label' to type 'System.Int32[,]'.

I need to store that because after clicking on the button the data will be disappeared.

Richard MacCutchan 22-May-20 8:19am

If your data is not a set of integers then you obviously don't declare the array as int type.

F-ES Sitecore 22-May-20 8:22am

Reading between the lines your data is the text of a label, but you'll need to parse that label and turn it into an array before storing it, .net can't do that for you.

F-ES Sitecore 22-May-20 8:30am

c# is case-sensitive, you have maticeA and MaticeA which is a bad idea. MaticeA is your array so that is what you need to store

Session["MyArray"] = MaticeA;

Petr Jaroš 22-May-20 8:30am

Thanks. I got that.