Compare Number of Rows affected - asp.net

Question

I'm trying to compare a string (network ID) and using a SQL Like command, return the numbers of rows affected (if the user name was found or not) however in my code I'm always getting " -1 " which i can not find why, the username is correct and found in the SQL table by running a query in SQL Server Mgt.
Try
Dim Con As New SqlConnection
Con.ConnectionString = "Data Source=WCRDUSMJEMPR9\SQLEXPRESS;Initial Catalog=MicroDB;Integrated Security=True"
Con.Open()
Dim SQL2 As String
SQL2 = "SELECT * from MicroDB_Users WHERE Users LIKE '+#Usercheck+'"
Dim cmd2 As New SqlCommand(SQL2, Con)
cmd2.Parameters.AddWithValue("#Usercheck", TextBox1.Text)
Dim obj2 = cmd2.ExecuteNonQuery
Con.Close()
If obj2 > 0 Then
MsgBox(obj2)
Response.Redirect("~\ControlCharts\AddData_Control.aspx")
Label7_Control.Visible = False
Else
MsgBox(obj2)
Label7_Control.Text = ("You are not authorized to Add Data")
Label7_Control.Visible = True
End If
Catch ex As Exception
MsgBox(Err.Description)
As you can see, i;m using a IF to compare if the user was found ( 1 row affected) or if it was not found ( 0 rows affected).

Answer 1

ExecuteNonQuery is used for insert,update or delete queries only. So you either have to use COUNT in your query and use ExecuteScalar or use ExecuteReader and the reader's HasRows property.
Using var reader = cmd2.ExecuteReader()
If reader.HasRows Then
' ...
Else
' ...
End If
End Using
ExecuteNonQuery:
For UPDATE, INSERT, and DELETE statements, the return value is the
number of rows affected by the command. When a trigger exists on a
table being inserted or updated, the return value includes the number
of rows affected by both the insert or update operation and the number
of rows affected by the trigger or triggers. For all other types of
statements, the return value is -1. If a rollback occurs, the return
value is also -1.
Update: Apart from that you're using the LIKE operator and the parameter incorrectly. Instead of
SQL2 = "SELECT * from MicroDB_Users WHERE Users LIKE '+#Usercheck+'"
cmd2.Parameters.AddWithValue("#Usercheck", TextBox1.Text)
use this approach
SQL2 = "SELECT * from MicroDB_Users WHERE Users LIKE #Usercheck"
cmd2.Parameters.AddWithValue("#Usercheck", string.Format("%{0}%", TextBox1.Text))

Answer 2

The number of rows affected is only returned when you do INSERT, DELETE, and UPDATE.
ExecuteNonQuery
For UPDATE, INSERT, and DELETE statements, the return value is the
number of rows affected by the command. When a trigger exists on a
table being inserted or updated, the return value includes the number
of rows affected by both the insert or update operation and the number
of rows affected by the trigger or triggers. For all other types of
statements, the return value is -1. If a rollback occurs, the return
value is also -1.
To get the number of rows, use SELECT count(*) FROM myTable
ExecuteNonQuery is meant for query that does not return rows, obvious from its name NonQuery.
For query that returns result, use these instead
ExecuteReader() - when multiple rows are returned
ExecuteScalar() - when one row and one column is returned. This will be perfect in your case

Answer 3

The number of rows is affected when you write INSERT UPDATE and DELETE scripts, not SELECT .. Use SQL2 = "SELECT * from MicroDB_Users WHERE Users LIKE '+#Usercheck+'" instead and cmd2.ExecuteScalar()
SQL2 = "SELECT COUNT(*) from MicroDB_Users WHERE Users LIKE '%" + TextBox1.Text + "%'";
Dim cmd2 As New SqlCommand(SQL2, Con)
cmd2.Parameters.AddWithValue("#Usercheck", TextBox1.Text)
Dim obj2 As Int32 = 0
obj2 = Convert.ToInt32(cmd2.ExecuteScalar())