数据库字段id,name,password
先发一第效果图

不多说直接给出代码
private void Form1_Load(object sender, EventArgs e)
{
//断开式连接数据库
SqlDataAdapter myDataAapter = new SqlDataAdapter("Select * From users", "data source=localhost;database=test;user id=sa;pwd=");
DataSet myDataSet = new DataSet();
//填充dataset映射表users
myDataAapter.Fill(myDataSet, "users");
dataGridView1.DataSource = myDataSet.Tables["users"];
//初始化赋第一行值
textBox1.Text = dataGridView1.Rows[dataGridView1.CurrentRow.Index].Cells["id"].Value.ToString();
textBox2.Text = dataGridView1.Rows[dataGridView1.CurrentRow.Index].Cells["name"].Value.ToString();
textBox3.Text = dataGridView1.Rows[dataGridView1.CurrentRow.Index].Cells["password"].Value.ToString();
}
private void dataGridView1_CellClick(object sender, DataGridViewCellEventArgs e)
{
//单击某一单元格获取当前的行赋于字段值
textBox1.Text =dataGridView1.Rows[dataGridView1.CurrentRow.Index ].Cells["id"].Value.ToString() ;
textBox2.Text = dataGridView1.Rows[dataGridView1.CurrentRow.Index].Cells["name"].Value.ToString();
textBox3.Text=dataGridView1.Rows[dataGridView1.CurrentRow.Index].Cells["password"].Value.ToString();
}