Combine 2 table data and fetch to Gridview dropdown list in ASP.net

SELECT a.EmpID, a.EmpName, a.EmpAddFROM , b.JobTitle, b.Salary
From Employee a,
INNER JOIN EmployeeSalary b
ON a.EmpID=b.EmpID;

CREATE TABLE EMPLOYEE
(
EmpId int primary key identity(1,1),
EmpName varchar(50),
EmpAdd varchar(50)
)


CREATE TABLE EmployeeSalary
(
EmpId int primary key identity(1,1),
JobTitle varchar(50),
Salary decimal(18,2)
)


SELECT A.EmpId,A.EmpName,A.EmpAdd,B.JobTitle,B.Salary FROM EMPLOYEE A ,EmployeeSalary B WHERE A.EmpId=B.EmpId

--If you need inner table based joins use this

SELECT A.EmpId,A.EmpName,A.EmpAdd,B.JobTitle,B.Salary FROM EMPLOYEE A  INNER JOIN EmployeeSalary B ON A.EmpId=B.EmpId

--If you need left table based joins use this

SELECT A.EmpId,A.EmpName,A.EmpAdd,B.JobTitle,B.Salary FROM EMPLOYEE A LEFT JOIN EmployeeSalary B ON A.EmpId=B.EmpId

--If you need right table based joins use this

SELECT A.EmpId,A.EmpName,A.EmpAdd,B.JobTitle,B.Salary FROM EMPLOYEE A RIGHT JOIN EmployeeSalary B ON A.EmpId=B.EmpId

SELECT  E.EmpID, E.EmpName, ES.JobTitle, ES.Salary
FROM  Employee E,
                 EmployeeSalary ES
WHERE E.EmpID=ES.EmpID

SELECT  ES.EmpID, ES.JobTitle
FROM  EmployeeSalary ES
WHERE ES.EmpID=@EmpID

Protected void gv_OnRowDataBound(object sender, GridViewRowEventArgs e)
{
        if(e.Row.RowType==DataControlRowType.DataRow)
        {
                  int EmpId= Convert.ToInt32(((Lable)e.Row.FindControl("lblEmpId")).Text.ToString());
                  DataSet ds=//pass the EmpId as input parameter to above query and get the data from database and store it in DataSet.
                  ddlJobTitle.DataSource=ds;
                  ddlJobTitle.DataTextField="JobTitle";
                  ddlJobTitle.DataValueField="EmpId";
                  ddlJobTitle.DataBind();
        }
}

.aspx page:
  <-asp:GridView runat="server" ID="gvDemo" AutoGenerateColumns="true"  OnRowDataBound="gvDemo_RowDataBound" >
    <-Columns>   
     <-asp:TemplateField>
      <-ItemTemplate>
       <-asp:DropDownList runat="server" ID="DemoDDL" AutoPostBack="false"/>
      <-/ItemTemplate>
     <-/asp:TemplateField>         
    <-/Columns>
<-/asp:GridView>
.cs page:
DataTable dt = new DataTable();
protected void Page_Load(object sender, EventArgs e)
{
   IDataReader reader = null;
   SqlConnection con = new SqlConnection("Data Source=XYZ;Initial Catalog=DBNAME;User ID=USERNAME;Password=USERPWD");
   con.Open();
   SqlDataAdapter a = new SqlDataAdapter("SELECT  ES.EmpID, ES.JobTitle FROM  EmployeeSalary ES WHERE ES.EmpID=@YourDesiredEmpID", con);
   a.Fill(dt);
   gvDemo.DataSource = dt;
   gvDemo.DataBind();
}
protected void gvDemo_RowDataBound(object sender, GridViewRowEventArgs e)
{
 if (e.Row.RowType == DataControlRowType.DataRow)
  {
    DropDownList ddl = (DropDownList)e.Row.FindControl("DemoDDL");
    ddl.DataSource = dt;
    ddl.DataTextField = "JobTitle";
    ddl.DataValueField = "EmpId";
    ddl.DataBind();
  }
}

SELECT EmpID, EmpName, JobTitle, Salary from Employee, EmployeeSalary WHERE Employee.EmpID = EmployeeSalary.EmpID;

Select *  from 
from Employee 
inner join EmployeeSalary  on Employee.Empid=EmployeeSalary.EmpID

select DISTINCT  JobTitle from EmployeeSalary

private void BindGridView()
{
    string strCon = ConfigurationManager.ConnectionStrings["CConnectionString"].ToString();
    SqlConnection conn = new SqlConnection(strCon);
    conn.Open();
    SqlDataAdapter da = null;
    DataSet ds = new DataSet();
    try
    {
        string strSql = "SELECT  Emp.EmpID, Emp.EmpName, ESal.JobTitle, ESal.Salary FROM  Employee Emp, EmployeeSalary ESal WHERE Emp.EmpID=ESal.EmpID";
        da = new SqlDataAdapter(strSql, conn);
        da.Fill(ds, "SampleTable");

        GridView2.DataSource = ds.Tables["SampleTable"].DefaultView;
        GridView2.DataBind();
        
    }
    catch (Exception ex)
    {
        lblError.Text = "Error!! <br>+" + ex.Message.ToString();
    }
    finally
    {
        ds.Dispose();
        da.Dispose();
        conn.Close();
        conn.Dispose();
    }
}

    <asp:DropDownList ID="Dtp1" runat="server" AutoPostBack="true" OnSelectedIndexChanged="Dtp1_SelectedIndexChanged" ></asp:DropDownList>
    <asp:Button ID="BtnSubmit" runat="server" Text="Click" OnClick="BtnSubmit_Click" />
        <asp:GridView ID="grd1" runat="server" >
        </asp:GridView>

SqlConnection sqlcon = new SqlConnection("Data Source=PCNAME;Initial Catalog=DBNAME;Integrated Security=True;");
            sqlcon.Open();
            SqlDataAdapter sqladp = new SqlDataAdapter("SELECT Id,EMPID FROM TblEmployee", sqlcon);
            sqladp.Fill(Dt);
            Dtp1.DataSource = Dt;
            Dtp1.DataTextField = "EMPID";
            Dtp1.DataValueField = "Id";
            Dtp1.DataBind();

 SqlConnection sqlcon = new SqlConnection("Data Source=PCNAME;Initial Catalog=DBNAME;Integrated Security=True;");
            sqlcon.Open();
            SqlDataAdapter sqladp = new SqlDataAdapter("SELECT Id,EmpName,EmpGender,EMPID,EMPIDCHAR,DeptId,DeptName from TblEmployee,Dept where EMPID=DeptID and EMPID="+ Convert.ToInt32(Dtp1.SelectedItem.Text), sqlcon);
            sqladp.Fill(Dt);
            grd1.DataSource = Dt;
            grd1.DataBind();

Protected void ddl_SelectedIndexChanged(object sender, EventArgs e)
{
           Bind_GridView();
}
Protected void Bind_GridView()
{
          DataSet ds=//pass dropdown selected value as input parameter and get data from database.
          gv.DataSource=ds;
          gv.DataBind();
}