operator += cannot be applied with string and void asp.net

FOLLOWING ERROR IS COMING

on this below line

ResultValue +=Convert.ToString(this.InsertRows(s_No, v_Name, rate, s_liter, entryDate);
below is whole code
DataTable dt = (DataTable)ViewState["dt"];
string s_No, v_Name, rate, s_liter, entryDate, ResultValue = Convert.ToString(0);
foreach (DataRow row in dt.Rows)
{
s_No = (row["S_No"].ToString());
v_Name = (row["V_Name"].ToString());
rate = (row["Rate"].ToString());
s_liter = (row["S_liter"].ToString());
entryDate = (row["EntryDate"].ToString());
ResultValue +=Convert.ToString(this.InsertRows(s_No, v_Name, rate, s_liter, entryDate);
}
if (ResultValue == dt.Rows.Count)
{
// Response.Redirect("BalePack.aspx");
Response.Redirect("Packrpt.aspx?PID=" + I_ID + "");
}
else
{
Response.Write("");
}
}
}
private void InsertRows(string s_No, string v_Name, string rate, string s_liter, string entryDate)
{
//con.Open();
using (SqlCommand cmd = new SqlCommand("Sp_InsertInvM", con))
{
cmd.Parameters.AddWithValue("@Action", "INSERTD");
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.AddWithValue("@I_ID", I_ID);
cmd.Parameters.AddWithValue("@S_Date", entryDate);
cmd.Parameters.AddWithValue("@S_No", s_No);
cmd.Parameters.AddWithValue("@P_Price", rate);
cmd.Parameters.AddWithValue("@S_Liter", s_liter);
con.Open();
cmd.ExecuteNonQuery();
ScriptManager.RegisterStartupScript(this, this.GetType(), "alert", " alert('Duplicate Order Save SuccessFully.'); window.open('SOgvud.aspx');", true);
con.Close();

2 Replies

Know the answer? Post it — somebody with the same question will find it here.

Jignesh Kumar6y ago
Accepted answer
Hi,

You are trying to convert void type to string and appliyed += operator which will not work because InsertRows() method return type is void means it will not return any value. If you want to return number of records inserted then you need to store values cmd.ExecuteNonQuery(); this to some variable and need to return from InsertRows() method.
Salman Beg6y ago
Hi. As per the error message it is saying that you can't apply += operator with string and void which means one of the value is void in that statement. Just put a breakpoint and check where exactly it is coming void value. Thanks.