1

I have code below which i use to select data from sql database table using dataadapter but i throws an error:

"Must declare the scalar variable"@UserName"

Where is the mistake in code????

I have tried the code below which throws an error "Must declare the scalar variable"@UserName" 

 Dim Query as string ="SELECT *FROM UserLogins WHERE [Login Name]= 
 @Username  AND Password=@passcode"

 // add parameters to dataadapter select command
 SQL.da.SelectCommand.Parameters.AddWithValue("@Username", "%" + 
 txtuserName.Text + "%")
 SQL.da.SelectCommand.Parameters.AddWithValue("@passcode", "%" + 
 txtpasslogin.Text + "%")

  //execute query and fill dataset
        da = New SqlDataAdapter(Query,Con)           
        cb = New SqlCommandBuilder(da)
        ds = New DataSet
        da.Fill(ds)
 Datagridview1.Datasource=ds.tables(0)
Improve this question
5
  • You are adding parameters to the da.SelectCommand object, then creating a new da object, so no, there aren't any parameters anymore. Commented Apr 8, 2019 at 19:23
  • thanks for the comment may you please use code to clarify your answer. Commented Apr 8, 2019 at 19:40
  • 1
    Try adding the parameters after you create the new adapter. Commented Apr 8, 2019 at 19:41
  • 2
    What are the % signs for? This isn't Like its =. Commented Apr 8, 2019 at 20:31
  • 3
    @Mary Username and password? Eh, close enough, come on in. Commented Apr 8, 2019 at 20:40

1 Answer 1

Reset to default
1

Whew, ok, there's a lot of weird things going on with this code.

First. Two Slashes (//) is not how comments are done in VB.NET. That's C# syntax. Use the single quote instead (')

Next, the error you received is an error coming from SQL Server.

"Must declare the scalar variable @UserName"

LarsTech specifically mentioned in his comment that the code you provided is adding the variables first and then creating a new instance of the SQLDataAdapter right after. If you modify your code to create the data adapter first, and then populate the variables, you should get a better result.

I'm not going to assume that the variables da, cb, and ds are already declared, but that the variable Con is declared somewhere.

Dim Query as string ="SELECT * FROM UserLogins WHERE [Login Name]=     
@Username  AND Password=@passcode"

'Note that I moved these two lines up here and made sure they were properly declared
Dim da as New SqlDataAdapter(Query,Con)           
Dim cb as New SqlCommandBuilder(da)

' add parameters to dataadapter select command
da.SelectCommand.Parameters.AddWithValue("@Username", "%" + 
    txtuserName.Text + "%")
da.SelectCommand.Parameters.AddWithValue("@passcode", "%" + 
    txtpasslogin.Text + "%")

' execute query and fill dataset

ds = New DataSet
da.Fill(ds)
Datagridview1.Datasource=ds.tables(0)

Finally, your sql statement should also have a space between the * and the FROM, and as mentioned by Mary in comments, the % signs are not necessary here because you aren't doing a like.

Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.