Reference previous object created in loop to update SQL

问题

I have a loop that sets up the form, which is the following code (in the form load event). This displays a checkbox with the persons name. It checks the checkbox if a bit field is 1.

int xAxisCheckbox = 130;
int yAxisCheckbox = 30;

for (int i = 0; i < selectDS.Tables[0].Rows.Count; i++)
{
    this.myCheckBox = new CheckBox();
    myCheckBox.Location = new Point(xAxisCheckbox, yAxisCheckbox);
    myCheckBox.Size = new Size(120, 20);
    myCheckBox.Text = selectDS.Tables[0].Rows[i]["FullName"].ToString();
    myCheckBox.Checked = (bool)selectDS.Tables[0].Rows[i]["InOperation"];
    yAxisCheckbox = yAxisCheckbox + 80;
}

Later on in the code (for a save button click event), it runs the same select but also a load of updates to set the InOperation field to true/false depending on the tick. It also resets the OperationOrder if you are being added to the Operation.

for (int i = 0; i < selectDataSet.Tables[0].Rows.Count; i++)
{
     userID = (int)selectDataSet.Tables[0].Rows[i]["UserID"];
     if (myCheckBox.Checked)
     {
         connection.runUpdate("UPDATE Users SET InOperation = 1, OperationOrder = CASE WHEN OperationOrder = 1 THEN 1 ELSE CASE WHEN InOperation=1 THEN OperationOrder ELSE (SELECT COUNT(*)+1 FROM Users WHERE InOperation=1 AND OperationOrder > 0) END END WHERE UserID=" + userID);
         connection.runUpdate("UPDATE Users SET OperationOrder = CASE WHEN OperationOrder = 0 THEN (SELECT COUNT(*) FROM Users WHERE InOperation=1) ELSE OperationOrder END WHERE InOperation=1");
      }
      else
      {
          connection.runUpdate("UPDATE Users SET InOperation = 0, OperationOrder = 0 WHERE UserID=" + userID);
          connection.runUpdate("UPDATE Users SET OperationOrder = CASE WHEN OperationOrder -1 = 0 THEN (SELECT COUNT(*) FROM Users WHERE InOperation=1) ELSE OperationOrder -1 END WHERE InOperation=1");
       }
   }

The problem with this is that it updates every single row based upon the last object created (e.g. if 5 rows, only the bottom checkbox would count for running the SQL, and it applies to all of them). How can I update every single row, is there a way I can reference each object I create rather than just the last one created?

UPDATE: Here is some of the new code that is causing errors. public partial class SelectUsers : Form { public int userID; public List myBoxes;

    public SelectUsers()
    {
        InitializeComponent();
    }

    private void SelectUsers_Load(object sender, EventArgs e)
    {
        DataSet ds = myconnection.runSelect(new DataSet(), "THE SELECT");

        int xAxisCheckbox = 40;
        int yAxisCheckbox = 50;

        myBoxes = new List<CheckBox>();

        for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
        {
            this.myCheckBox = new CheckBox();
            myCheckBox.Location = new Point(xAxisCheckbox, yAxisCheckbox);
            myCheckBox.Size = new Size(120, 20);
            myCheckBox.Text = ds.Tables[0].Rows[i]["FullName"].ToString();
            myCheckBox.Checked = (bool)ds.Tables[0].Rows[i]["InOperation"];
            yAxisCheckbox = yAxisCheckbox + 80;
            myBoxes.Add(myCheckBox);
        }
    }

    private void saveBtn_Click(object sender, EventArgs e)
    {
        DataSet ds = myconnection.runSelect(new DataSet(), "THE SELECT");

        for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
        {
            userID = (int)ds.Tables[0].Rows[i]["UserID"];
            if (myBoxes[i].Checked)
            {
                myconnection.runUpdate("UPDATE Users SET InOperation = 1, OperationOrder = CASE WHEN OperationOrder = 1 THEN 1 ELSE CASE WHEN InOperation=1 THEN OperationOrder ELSE (SELECT COUNT(*)+1 FROM Users WHERE InOperation=1 AND OperationOrder > 0) END END WHERE UserID=" + userID);
                myconnection.runUpdate("UPDATE Users SET OperationOrder = CASE WHEN OperationOrder = 0 THEN (SELECT COUNT(*) FROM Users WHERE InOperation=1) ELSE OperationOrder END WHERE InOperation=1");
            }
            else
            {
                myconnection.runUpdate("UPDATE Users SET InOperation = 0, OperationOrder = 0 WHERE UserID=" + userID);
                myconnection.runUpdate("UPDATE Users SET OperationOrder = CASE WHEN OperationOrder -1 = 0 THEN (SELECT COUNT(*) FROM Users WHERE InOperation=1) ELSE OperationOrder -1 END WHERE InOperation=1");
            }
        }
    }

回答1:

You should keep an array of checkboxes rather than just an individual checkbox

int xAxisCheckbox = 130;
int yAxisCheckbox = 30;

List<CheckBox> myBoxes = new List<CheckBox>();

for (int i = 0; i < selectDS.Tables[0].Rows.Count; i++)
{
    this.myCheckBox = new CheckBox();
    myCheckBox.Location = new Point(xAxisCheckbox, yAxisCheckbox);
    myCheckBox.Size = new Size(120, 20);
    myCheckBox.Text = selectDS.Tables[0].Rows[i]["FullName"].ToString();
    myCheckBox.Checked = (bool)selectDS.Tables[0].Rows[i]["InOperation"];
    yAxisCheckbox = yAxisCheckbox + 80;
    myBoxes.Add(myCheckBox);
}

And later ir your for loop:

for (int i = 0; i < selectDataSet.Tables[0].Rows.Count; i++)
{
     userID = (int)selectDataSet.Tables[0].Rows[i]["UserID"];
     if (myBoxes[i].Checked)
     {
         connection.runUpdate("UPDATE Users SET InOperation = 1, OperationOrder = CASE WHEN OperationOrder = 1 THEN 1 ELSE CASE WHEN InOperation=1 THEN OperationOrder ELSE (SELECT COUNT(*)+1 FROM Users WHERE InOperation=1 AND OperationOrder > 0) END END WHERE UserID=" + userID);
         connection.runUpdate("UPDATE Users SET OperationOrder = CASE WHEN OperationOrder = 0 THEN (SELECT COUNT(*) FROM Users WHERE InOperation=1) ELSE OperationOrder END WHERE InOperation=1");
      }
      else
      {
          connection.runUpdate("UPDATE Users SET InOperation = 0, OperationOrder = 0 WHERE UserID=" + userID);
          connection.runUpdate("UPDATE Users SET OperationOrder = CASE WHEN OperationOrder -1 = 0 THEN (SELECT COUNT(*) FROM Users WHERE InOperation=1) ELSE OperationOrder -1 END WHERE InOperation=1");
       }
   }

That should do it.

It goes without saying, that executing SQL statements directy in your form is not a good idea, but thats another story

回答2:

Wouldn't it be A LOT faster if you could simply loop over all the checkboxes on your form, build a SQL update script from there and do a .runUpdate() of said script in the end ?

Things that come to mind :

make sure to use a stringBuilder
first part update the InOperation field only
then update the OperationOrder in 1 single UPDATE

You'll need a way to link the checkbox with the relevant UserId off course.

回答3:

Carlos Grappa answer was pointing me in the right direction by saying use an array, but it was setup wrong. After reading through programming books, I found that you create an array as follows:

// Global
CheckBox[] myCheckBox;
DataSet ds;

private void SelectUsers_Load(object sender, EventArgs e) {

    ds = myconnection.runSelect(new DataSet(), "THE SELECT");

    int xAxisCheckbox = 40;
    int yAxisCheckbox = 50;

    // Create the CheckBox array (amount based on number of rows)
    myBoxes = new CheckBox[ds.Tables[0].Rows.Count];

    for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
    {
        // Create a new Checkbox
        myCheckBox[i] = new CheckBox();

        myCheckBox.Location = new Point(xAxisCheckbox, yAxisCheckbox);
        myCheckBox.Size = new Size(120, 20);
        myCheckBox.Text = ds.Tables[0].Rows[i]["FullName"].ToString();
        myCheckBox.Checked = (bool)ds.Tables[0].Rows[i]["InOperation"];
        yAxisCheckbox = yAxisCheckbox + 80;

        // Add the Checkbox
        Controls.Add(myCheckBox[i]);
    }
}

private void saveBtn_Click(object sender, EventArgs e) {
    for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
    {
        userID = (int)ds.Tables[0].Rows[i]["UserID"];

        if (myBoxes[i].Checked)
        {
            myconnection.runUpdate("UPDATE Users SET InOperation = 1, OperationOrder = CASE WHEN OperationOrder = 1 THEN 1 ELSE CASE WHEN InOperation=1 THEN OperationOrder ELSE (SELECT COUNT(*)+1 FROM Users WHERE InOperation=1 AND OperationOrder > 0) END END WHERE UserID=" + userID);
            myconnection.runUpdate("UPDATE Users SET OperationOrder = CASE WHEN OperationOrder = 0 THEN (SELECT COUNT(*) FROM Users WHERE InOperation=1) ELSE OperationOrder END WHERE InOperation=1");
        }
        else
        {
            myconnection.runUpdate("UPDATE Users SET InOperation = 0, OperationOrder = 0 WHERE UserID=" + userID);
            myconnection.runUpdate("UPDATE Users SET OperationOrder = CASE WHEN OperationOrder -1 = 0 THEN (SELECT COUNT(*) FROM Users WHERE InOperation=1) ELSE OperationOrder -1 END WHERE InOperation=1");
        }
    }
}

Deroby you are probably right, however I do not know how to do this.

来源：https://stackoverflow.com/questions/14760263/reference-previous-object-created-in-loop-to-update-sql

标签

sql

object

checkbox