Else Condition in Foreach Loop on DataGridView Not Working

Question

I wonder if you can give me a push in the right direction - I have some C# code and have two DataGridViews ()dgv1 and dgv2). When a button is pressed, the dataGridViews are filled (by way of a Datatable as the source) from two different databases. Both DataGridViews have the same number of columns and I am using column 4 (cell 3) to check if a row in dgv1 has the same value in cell 3 as any of the rows in dgv2. What I am trying to achieve is;

if a row is selected in dgv1 and there is a matching row (same value in cell 3), then the row is automatically highlighted in dgv2
when the selection is changed in dgv1, the same happens i.e. the foreach loop checks dgv2 to find a match
if a selected row in dgv1 does not have a match in dgv2, I want to display a messagebox stating "no match"

Now, I wrote the code in the SelectionChanged event of the dgv1 and the foreach is working fine, and does exactly what I want....until I put an else condition. When I put the else condition, the message box is displayed each time a selection is made in dgv1, even if there IS a match. What I need is for the message box to only appear if there is no match between dgv1 and dgv2. Below is my code;

private void dgv1_SelectionChanged(object sender, EventArgs e)
        {

            this.dgv2.ClearSelection();
            this.dgv2.Tag = "";
            txtBxID.Text = "";
            
            foreach (DataGridViewRow dgv2row in dgv2.Rows)
            {

                if (dgv1.CurrentRow.Cells[3].Value.ToString() == Convert.ToString(dgv2row.Cells[3].Value))
                {
                    
                    dgv2.Selected = true;
                    txtBxID.Text = dgv2.Cells[6].Value.ToString();
                    dgv2.Tag = dgv2row.Cells[6].Value.ToString();
                    MessageBox.Show(Convert.ToString(dgv2.Tag));
                    
                }
            
            
               else
                {
                    MessageBox.Show("no match");
                }
            }

        }

I hope this all makes sense, and a thousand apologies if this same or similar question has been asked. I am still trying to familiarise myself with StackOverflow.

EDIT: following the two answers by @KlausGütter and @KostandinVllahu, I have attempted to add a Boolean variable as shown below. This has solved half the problem, though. What happens now is - when the button is clicked (to fill the dataGridViews) the message box showing "no match" is displayed repeatedly about 5 times (presumably for each row to be added to the dataGridViews, that is 5 in this case), and once I've clicked OK on the message boxes and they've disappeared, the code does what I want it. Where am I going wrong with the Boolean? Have I misplaced it? I have done the below;

private void dgv1_SelectionChanged(object sender, EventArgs e)
        {

                      
            this.dgv2.ClearSelection();
            this.dgv2.Tag = "";
            txtBxID.Text = "";
            
            Boolean match = false;
            
            foreach (DataGridViewRow dgv2row in dgv2.Rows)
            {

                if (dgv1.CurrentRow.Cells[3].Value.ToString() == Convert.ToString(dgv2row.Cells[3].Value))
                {
                    match = true;  
                    dgv2.Selected = true;
                    txtBxID.Text = dgv2.Cells[6].Value.ToString();
                    dgv2.Tag = dgv2row.Cells[6].Value.ToString();
                    MessageBox.Show(Convert.ToString(dgv2.Tag));
                    
                }
            
            }
               if (!match)
                {
                    MessageBox.Show("no match");
                }
            

        }

Many Thanks in Advance.

user_1410664 · Answer

MessageBoxes are, in general, pretty annoying. It won't take long for you to become tired of having to dismiss a "No match" messagebox as you click around the grid. Think how annoying it is having to dismiss the box 5 times at the moment, and that's doable by keeping your mouse in the same place and going click click click click click. It gets more wearisome as you're trying to work, clicking on cells in dgv1 and then keep having to trek to the middle of the screen, dismiss "No match", go back and click another cell, dismiss "No match" again

Instead let's show and hide a label, that you can make bold big red if you want. The label coming and going doesn't interrupt the user work flow. Try to avoid using messageboxes at all...

The good thing about the label is we can show it at the start of the operation, hide it if we find a row and don't hide it if we don't. This means at the end of the operation it is always in the state we want. It implicitly includes our Boolean logic

    private void dgv1_SelectionChanged(object sender, EventArgs e)
    {         
        this.dgv2.ClearSelection();
        this.dgv2.Tag = "";
        txtBxID.Text = "";
        noMatchWarningLabel.Visible = true;

        var lookingFor = dgv1.CurrentRow.Cells[3].Value.ToString();
        
        foreach (DataGridViewRow dgv2row in dgv2.Rows)
        {
            if (lookingFor == Convert.ToString(dgv2row.Cells[3].Value))
            {
                dgv2row.Selected = true;
                dgv2.Tag = txtBxID.Text = dgv2row.Cells[6].Value.ToString();
                noMatchWarningLabel.Visible = false;
            }
        }
    }

Else Condition in Foreach Loop on DataGridView Not Working

1 Answers