Como carregar dados na caixa de texto da tabela de banco de dados sql

Oh o que. Pare!!! Use a consulta parametrizada para evitar SQL Injection

Mencione sua string de conexão em connection

Espero que o problema seja que você tenha perdido txtEmployId.Text value e txtEmplyName.Text valor em sua consulta de seleção

SqlConnection  connection= new SqlConnection(your Connection string);
string query = "SELECT CNIC, City, MobileNo, Address, Salary, DailyWage, Status   
       FROM  Employees WHERE EmployId [email protected] AND Emplname = @Emplname ";
SqlCommand  command1 = new SqlCommand(query, connection); 
connection.Open();
command1.Parameters.AddWithValue("@EmpID",txtEmployId.Text);
command1.Parameters.AddWithValue("@Emplname",txtEmplyName.Text);
SqlDataReader reader1 = command1.ExecuteReader();


    while(reader1.Read())
   {
    this.txtCNIC.Text = (reader1["CNIC"].ToString());
    this.txtEmplyCity.Text = (reader1["City"].ToString());
    this.txtEmplyAddress.Text = (reader1["Address"].ToString());
    this.txtSalary.Text = (reader1["Salary"].ToString());
    this.txtDailyWage.Text = (reader1["DailyWage"].ToString());

        reader1.Close();
    }