Erro: Incorrect syntax near '='.

Question

Boa tarde,

Quando tento executar essa funcção

Function Mostra_usuario(ByVal nome As String) As Boolean
        Dim usuario As New DataTable
        Dim Strcon As String
        Strcon = "Data source=.\UBERCONTA;AttachDbFilename=C:\Arquivos de programas\Microsoft SQL Server\MSSQL10.UBERCONTA\MSSQL\DATA\simples.mdf;Integrated Security=True;User Instance=True"
        Dim con As New SqlConnection(Strcon)
        Dim Sql = New SqlCommand("SELECT codigo, nome, senha from usuario WHERE codigo=" + txtUsuario.Text)

        Try
            con.Open()
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try

        sql.Connection = con
        Dim Dr As SqlDataReader = Sql.ExecuteReader

        While Dr.Read
            txtNome.Text = Dr.GetString(0).ToString()
        End While
        Return 1
        Exit Function
    End Function

Dá o seguinte Erro:   Incorrect syntax near '='.