Error on sql database “Must declare the scalar variable”

Question

I have a problem with my login system. I made a simple system which worked well, but I wanted to make it more advanced and display a different start page depending on a user

Answer 1

You have passed in @Login and @Password as parameters to your query, but you have not passed in @UserType as a parameter to your query.

Answer 2

As the error states: Must declare the scalar variable "@UserType"

In other words, the SQL command has a parameter for @UserType, but there are no parameters declared in the parameters collection.

SqlCommand cmd = new SqlCommand(
"select * from dbo.UserInfo where Login =@Login and UserType=@UserType and Password=@Password and UserType=@UserType", con);
cmd.Parameters.AddWithValue("@Login", txtUserName.Text);
cmd.Parameters.AddWithValue("@Password", txtPWD.Text+".123");

Add another parameter for the @UserType parameter:

cmd.Parameters.AddWithValue("@UserType", "User Type");

Also, the SQL contains a duplicate reference to for @UserType:

select * from dbo.UserInfo 
where Login=@Login 
      and UserType=@UserType 
      and Password=@Password 
      and UserType=@UserType

Should probably be:

select * from dbo.UserInfo 
where Login=@Login 
      and Password=@Password
      and UserType=@UserType