标量 Function SQL 来自 Linq Z6145AFC977C7660083BDCDDEAZ1B7D9

Question

I have a Function in Sql For check if username and password is Correct return 1 or 0

CREATE Function [dbo].[checklogin](@user varchar(30),@pass varchar(30))
Returns  BIT  
AS 
BEGIN  
DECLARE @check as bit
if (SELECT count(*) from dbo.Users where dbo.USERS.user_name= @user and  dbo.USERS.user_password=@pass)=1
set @check = 1
else
set @check=0
Return @check
END  

when call this function without Sql linq Return Real information

  Sub loginCheck(ByVal username As String, ByVal password As String, ByVal frm As Form)

        Using con As New SqlConnection(inform.connectionstring)//
            con.Open()
            Using cmd As New SqlCommand("select dbo.checklogin('Manager','123');", con)
                Dim a As Boolean = CBool(cmd.ExecuteScalar)
                If a Then
                    MsgBox("Success")
                Else
                    MsgBox("Failed")
                End If
            End Using

        End Using
    End Sub

but when i need using linq return false always

   Sub loginCheck(ByVal username As String, ByVal password As String, ByVal frm As Form)

        Using con As New SqlConnection(inform.connectionstring)
            con.Open()
            Dim dta As New DataAj
            Dim ab As Boolean = dta.checklogin(username, password).Value
            If ab Then
                MsgBox("Success")
            Else
                MsgBox("Failed")
            End If

        End Using
    End Sub

Answer 1

This simple function can be used to get value from exactly one field one record query result

Public Function getDataScalar(ssql As String)
    openConnection()

    Try
        Dim q As New MySqlCommand

        q.Connection = db
        q.CommandText = ssql
        getDataScalar = q.ExecuteScalar

    Catch ex As Exception
        'Exception
    End Try
End Function

How to use it:

Dim userid as String = getDataScalar("select username from user where userid=99")

Variable 'username' would be filled with the value of field username as a result from that query.