how to show only data from textboxs to the gridview in c#

I think you mean something like this ...

dataGridView1.Rows.Add(textBox1.Text, textBox2.Text, textBox3.Text, textBox4.Text);

This assumes that the Columns collection of the dataGridView was set up at design time

I've also seen your other question that said there were 8 text boxes... the better route would be to do something like this ...

DataTable dt = new DataTable("myTable");
dt.Columns.Add("column1", typeof(string));
dt.Columns.Add("column2", typeof(string));
dt.Columns.Add("column3", typeof(string));
dt.Columns.Add("column4", typeof(string));
dt.Rows.Add(textBox1.Text, textBox2.Text, textBox3.Text, textBox4.Text);
dataGridView1.DataSource = dt;

where the Columns collection of the dataGridView is empty at design time.