No mapping exists from object type System.Text.StringBuilder to a known managed provider native type

Question

I am try to create an application using asp.net (c#) In which the user will upload a single file (any data format doc, docx,pdf) using fileupload control.

And then I have to save the contents of the file in the database selected by the user. The structure of database is:

Field              DataType
id                 int
title              nvarchar(MAX)
body               varbinary(MAX)
bodyoverview       nvarchar(MAX)
postedon           date

The contents of the file will be saved in body attribute. Also I have the following code:

 protected async void Button_Upload_Click(object sender, EventArgs e)
        {
            StringBuilder stringBuilder = new StringBuilder();
            if(FileUpload1.HasFile)
            {
                try
                {
                    string FileContent = String.Empty;
                    using(StreamReader inputStreamReader=new StreamReader(FileUpload1.PostedFile.InputStream))
                    {
                        FileContent = await inputStreamReader.ReadToEndAsync();
                        
                        foreach (char c in FileContent.ToCharArray())
                        {
                            stringBuilder.Append(Convert.ToString(c, 2).PadLeft(8, '0'));
                        }
                    }
                    SqlConnection sqlConnection = new SqlConnection("Data Source=(localdb)\\ProjectsV12;Initial Catalog=Blog;Integrated Security=True");
                    string query = "insert into blogthumbnails values(@blogtitle,@body,@bodyoverview,@allowcomments,@commentscount,@postedon)";
                    SqlCommand sqlCommand = new SqlCommand(query, sqlConnection);
                    sqlCommand.Parameters.AddWithValue("@blogtitle", TextBox_Title_Of_The_Blog.Text);
                    sqlCommand.Parameters.AddWithValue("@body", stringBuilder);
                    sqlCommand.Parameters.AddWithValue("@postedon", DateTime.Now.Date);
                    await sqlConnection.OpenAsync();
                    try
                    {
                        int i = sqlCommand.ExecuteNonQuery();
                        if(i>0)
                        {
                            Label_File_Upload_Status.Text = "File Uploaded";
                        }
                        else
                        {
                            Label_File_Upload_Status.Text = "Please try again";
                        }
                    }
                    catch(SqlException sqlException)
                    {
                        Label_File_Upload_Status.Text = sqlException.Message.ToString();
                    }
                }
                catch(Exception FileUploadException)
                {
                    Label_File_Upload_Status.Text = "Error in uploading file. Please try again. Error: "+FileUploadException.Message;
                }
            }
            else
            {
                Label_File_Upload_Status.Text = "Please select a file to upload";
            }
        }

But I am getting the error:

No mapping exists from object type System.Text.StringBuilder to a known managed provider native type.

Answer 1

By default StringBuilder is not a native type that can be mapped to NVARCHAR, TEXT, INT, DEC or other native sql types.

try these:

 sqlCommand.Parameters.AddWithValue("@body", stringBuilder.ToString());

Answer 2

Since body is of varbinary type thus data should be in binary format. You need to convert the result from stringBuilder into byte array first and then you can save it in you table.

byte[] byteArray = Encoding.UTF8.GetBytes(Convert.ToString(stringBuilder));    
sqlCommand.Parameters.AddWithValue("@body", byteArray);

Answer 3

This line: sqlCommand.Parameters.AddWithValue("@body", stringBuilder); should be

sqlCommand.Parameters.AddWithValue("@body", stringBuilder.ToString());