How can I check if column value same on every row on GridView?

Question

I have a grid view with 10 rows.

After clicking on a button I would like to check and make sure each cell value are the same or not under the firstname column of gridview .

If all the cell values are same then call the changeCellValues() method. If any cell value is different then MessageBox.Show("You cant use your method");

private void button1_Click(object sender, EventArgs e)
{ 
    string x;
    string y;

    x = dataGridView1.Rows[0].Cells[1].Value.ToString();

    for (int i = 0; i < 11; i++)
    {
        y = dataGridView1.Rows[i].Cells[1].Value.ToString();
        if (x == y) continue;
        MessageBox.Show("You cant use your method");
    }
}

How can I check if column value same on every row on GridView?

Answer 1

If you have 10 rows, change i < 11 to i < 10 and start i from 1 because you already get the first row's value and store it into x .Your way seems correct but instead of displaying the messagebox inside of the loop, you can use something like this:

x = dataGridView1.Rows[0].Cells[1].Value.ToString();
bool control = true;
for (int i = 1; i < 10; i++)
{
   y = dataGridView1.Rows[i].Cells[1].Value.ToString();
   if (x != y) { control = false; break; }
}

if(!control)  MessageBox.Show("You cant use your method");
else changeCellValues();

Answer 2

Alternative using LINQ... grab everything in the column "firstname", remove duplicates using Distinct , and then count the number of unique names. (If you have more than 1 unique name, they're not all the same.)

var isSameName = dataGridView1.Rows.Cast<DataGridViewRow>()
                              .Select(x => Convert.ToString(x.Cells["firstname"].Value))
                              .Distinct().Count() == 1;

if (!isSameName)
{
    MessageBox.Show("You cant use your method");
    return;
}

changeCellValues();