System.InvalidCastException: Unable to cast object of type 'System.String' to type 'System.Byte[]'.

Hi All,

I am trying to retrieve a Picture from an SQL 2005 database. Here is my code:

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load Dim ListingID As String = (Request.QueryString("GUID"))

'Connect to the database and bring back the image contents & MIME type for the specified picture

Using myConnection As New SqlConnection(ConfigurationManager.ConnectionStrings("ConnectionStringListings").ConnectionString)

Const SQL As String = "SELECT [Pic1Ext], [Picture1] FROM [Listings] WHERE [ListingID] = @ListingID"

Const SQL As String = "SELECT [Pic1Ext], [Picture1] FROM [Listings] "Dim myCommand As New SqlCommand(SQL, myConnection)myCommand.Parameters.AddWithValue("@ListingID", ListingID)

myConnection.Open()

Dim myReader As SqlDataReader = myCommand.ExecuteReader

If myReader.Read Then

Response.ContentType = myReader("Pic1Ext").ToString() Response.BinaryWrite(myReader("Picture1"))

End If

myReader.Close()

myConnection.Close()

End Using

End Sub

And I am getting the following error and I am not sure what it means??

 Exception Details: System.InvalidCastException: Unable to cast object of type 'System.String' to type 'System.Byte[]'.

Source Error:

Line 22:             If myReader.Read Then
Line 23:                 Response.ContentType = myReader("Pic1Ext").ToString()
Line 24:                 Response.BinaryWrite(myReader("Picture1"))
Line 25:             End If
Line 26:             myReader.Close()

Source File: D:\inetpub\rentication\Rentication0\RegisteredUsers\ShowPicture.aspx.vb    Line: 24

 

I know I have a picture uploaded but I keep getting this error. Help?

0
istakoza
5/5/2008 5:18:59 AM
asp.net.visual-basic.net 3721 articles. 0 followers. Follow

3 Replies
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what is the datatype of [Picture1] in [Listings] table? it should be of type "image"..

Public Sub Page_Load(sender As Object, e As EventArgs)

        Dim myConnection As New SqlConnection(ConfigurationSettings.AppSettings("ConnectionString"))
        Dim myCommand As New SqlCommand("Select * from Person", myConnection)

        Try
            myConnection.Open()
            Dim myDataReader as SqlDataReader
            myDataReader = myCommand.ExecuteReader(CommandBehavior.CloseConnection)

            Do While (myDataReader.Read())
                Response.ContentType = myDataReader.Item("PersonImageType")
                Response.BinaryWrite(myDataReader.Item("PersonImage"))
            Loop

            myConnection.Close()
            Response.Write("Person info successfully retrieved!")
        Catch SQLexc As SqlException
            Response.Write("Read Failed : " & SQLexc.ToString())
        End Try

    End Sub

 


Thanx,
[KaushaL] || BloG || Profile || Microsoft MVP

"I would love to change the world, but they won’t give me the source code"


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0
kaushalparik27
5/5/2008 7:49:03 AM

Thanks for responding,

I am using VS 2008 I don't believe that there is an image type in this platform, I am using nvarchar(max) in the database.

0
istakoza1
5/5/2008 3:00:37 PM

Ok I have an even bigger problem now. It turns out I have not been insertimg images properly, they have been inserting as string in my database in a row with type varchar(MAX). I no wunderstand that I have to make that row varbinary(Max). But when I do that I can't insert anything anymore. I think I have a discrepancy in variable types.

This is my code that sets the variable:

Dim imageBytes(F1.PostedFile.InputStream.Length) As Byte

F1.PostedFile.InputStream.Read(imageBytes, 0, imageBytes.Length)

e.Values("Picture1Data") = imageBytes

The SQL Parameter is defined like this:

<asp:Parameter Name ="Picture1Data" type="Object"/>

<asp:Parameter Name ="MIMEType1" />

 

When I have the "Type=Object" in the parameter control, I am able to insert other fields into the database but not Picture1?

When I remove it nothing inserts at all?

Any help, I hope I have explained my problem well enough.

0
istakoza
5/6/2008 5:04:25 AM
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