在文本框中检测第一个字母，然后出现在gridview中

Question

I'm a newbie in programming. How can I search the employee name by the first letter and display all those name which starts from eg: A then it should get display in data grid view? Currently, my code just detect 2 letters in textbox, then display in grid view. I want it detect the first letter. Here is my code:

private void textBoxName_KeyPress(object sender, KeyPressEventArgs e)
{
    con = new SqlConnection(cs);
    con.Open();
    adapt = new SqlDataAdapter(
        "select name, empno, workno from m_employee where name like '%" + 
        textBoxName.Text + "%' and not [recsts] = 'R' order by empno", con);
    dt = new DataTable();
    adapt.Fill(dt);
    dataGridView1.DataSource = dt;
    con.Close();

    if (textBoxName.Text != null)
    {
        dataGridView1.Visible = true;
    }

    if (textBoxName.Text == "")
    {
        dataGridView1.Visible = false;
    }

}

private void textBoxName_TextChanged(object sender, EventArgs e)
{
    textBoxName.Text = textBoxName.Text.TrimEnd();

    if (textBoxName.Text == "")
    {
        dataGridView1.Visible = false;
    }

    (dataGridView1.DataSource as DataTable).DefaultView.RowFilter = 
        string.Format("Name LIKE '%{0}%'", textBoxName.Text);
}

private void dataGridView1_CellMouseClick(object sender, DataGridViewCellMouseEventArgs e)
    {

            textBoxName.Text = dataGridView1.Rows[e.RowIndex].Cells["name"].Value.ToString();
            textBoxEmplNo.Text = dataGridView1.Rows[e.RowIndex].Cells["empno"].Value.ToString();
            textBoxWorkNo.Text = dataGridView1.Rows[e.RowIndex].Cells["workno"].Value.ToString();

        string selectSql = "select icnum, empno, passport, deptno, section from m_employee where workno=@workno";
        SqlCommand cmd = new SqlCommand(selectSql, con);
        cmd.Parameters.AddWithValue("@workno", textBoxWorkNo.Text);

        bool isDataFound = false;

        try
        {
            con.Open();

            using (SqlDataReader read = cmd.ExecuteReader())
            {

                while (read.Read())
                {
                    isDataFound = true;

                    textBoxICPass.Text = (read["icnum"].ToString());
                    textBoxPassport.Text = (read["passport"].ToString());
                    textBoxDept.Text = (read["deptno"].ToString());
                    textBoxSection.Text = (read["section"].ToString());

                    string imgFilePath = @"C:\Users\hamizah\Documents\Visual Studio 2013\WebSites\EV\photo\" + textBoxEmplNo.Text + ".jpg";
                    if (File.Exists(imgFilePath))
                    {
                        pictureBox1.Visible = true;
                        pictureBox1.Image = Image.FromFile(imgFilePath);
                    }
                    else
                    {
                        // Display message that No such image found
                        // MessageBox.Show("No Image Found");
                        pictureBox1.Visible = true;
                        pictureBox1.Image = Image.FromFile(@"C:\Users\hamizah\Documents\Visual Studio 2013\WebSites\EV\photo\No-image-found.jpg");
                    }


                }
            }
        }
        finally
        {
            con.Close();
        }


    }

Answer 1

If you only want to get the first letter of your specific text, you can do one of the following approaches to do so:

// Access the first character by it's index
var letter = YourTextBox.Text[0];

// Access the first letter via the Substring() method
var letter = YourTextBox.Text.Substring(0, 1);

Off-topic: Consider Parameterized Queries

Additionally, you should not use string concatenation when building your queries as it leaves you vulnerable to SQL Injection attacks. Consider instead using parameterized queries, which should keep you protected from those and may make your code a bit more readable:

// Build your query using parameters
var query = "SELECT ... WHERE Name LIKE @letter AND ...";

// Build your adapter to execute
var adapter = new SqlDataAdapter(query, connection);

// Add your parameter
adapter.SelectCommand.Parameters.AddWithValue("@letter", letter + "%");

// Execute it here