CODEWITHSUNDEEP
c#datatable
1aliff
1aliff

Reputation: 445

c# using previous datatable column value

In my project. I have a datatable and a button named 'Process'

After clicked the 'Process' button, my datatable column changed to a new value (as i coded below)

Is it possible to get those changed value back (before i clicked the button) because i need to display them together with the new value (when i click the button)

Here's what i coded so far:

        for (int l = 0; l < my_datatable.Rows.Count; l++)
        {
            data_source = my_datatable.Rows[l][3].ToString();

            if (data_source.Contains("Cross Site Scripting"))
            {
                my_datatable.Rows[l][3] = "2";
            }
            else if (data_source.Contains("SQL Injection"))
            {
                my_datatable.Rows[l][3] = "3";
            }
            else if (data_source.Contains("Unicode Attack"))
            {
                my_datatable.Rows[l][3] = "4";
            }
            else if (data_source.Contains("Proxy Attack"))
            {
                my_datatable.Rows[l][3] = "5";
            }
            else
            {
                my_datatable.Rows[l][3] = "1";
            }
        }

Upvotes: 0

Views: 1142

Answers (2)

Wheels73
Wheels73

Reputation: 2890

If you copy the datatable before you alter it you should be able to do it.

var dataCopy = my_datatable.Copy();

The only thing you'll have to do is to keep track of what fields in what row you you have changed.

Thinking about it, there may be a better solution using the some of the below. I can't recall the exact specifics without researching but they may be of some use.

 if (row.RowState == DataRowState.Modified)
 {
      var currentRow = row[0, DataRowVersion.Current];
      var previousRow = row[0, DataRowVersion.Proposed];
 }

You can then use this to get both values

Or there is also

 var modifiedTable = my_datatable.GetChanges(DataRowState.Modified)

Hello again... I've done a bit of experimentation and I believe the below will do what you need. It is based on a simple data table that I create to demonstrate.

            var data = new DataTable("Table1");
            data.Columns.Add(new DataColumn("Username", typeof(string)));
            data.Columns.Add(new DataColumn("UserId", typeof(int)));

            var row = data.NewRow();
            row["Username"] = "User1";
            row["Userid"] = 12356;
            data.Rows.Add(row);

            data.AcceptChanges();

            var originalTable = data.Copy();

            var rowToEdit = data.Rows[0];
            rowToEdit["Username"] = "User2";

            var rowPos = 0;

            foreach (DataRow dr in data.Rows)
            {
                if (dr.RowState == DataRowState.Modified)
                {
                    foreach (DataColumn c in dr.Table.Columns)
                    {
                        if (dr.ItemArray[c.Ordinal] != originalTable.Rows[rowPos].ItemArray[c.Ordinal] )
                        {
                            //Show Changed value
                            var x = originalTable.Rows[rowPos].ItemArray[c.Ordinal];
                        }
                    }
                }

                rowPos++;
            }

Thanks

Upvotes: 1

Nathangrad
Nathangrad

Reputation: 1464

var dictionary = new Dictionary<int, string>();
for (int l = 0; l < my_datatable.Rows.Count; l++)
{
    data_source = my_datatable.Rows[l][3].ToString();
    dictionary.Add(l, data_source);

    // ...
}
// Access:
dictionary[0] // Returns the previous string

I would choose to use a Dictionary<TKey, TValue> to store the strings based on their row index within the DataTable. By using the Dictionary<TKey, TValue>.Add(key, value) method, it stores it for later usage.

When accessing the string values from it, you can treat it as an associative array and just use Dictionary<TKey, TValue>[index].

Hope this helped!

Upvotes: 0

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