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MimeKit

TextPart Class

A Textual MIME part.
Inheritance Hierarchy
SystemObject
  MimeKitMimeEntity
    MimeKitMimePart
      MimeKitTextPart

Namespace: MimeKit
Assembly: MimeKit (in MimeKit.dll) Version: 4.3.0
Syntax
C#
public class TextPart : MimePart

The TextPart type exposes the following members.

Constructors
 NameDescription
Public methodTextPart Initialize a new instance of the TextPart class with a Content-Type of text/plain.
Public methodTextPart(MimeEntityConstructorArgs) Initialize a new instance of the TextPart class.
Public methodTextPart(String) Initialize a new instance of the TextPart class with the specified text subtype.
Public methodTextPart(TextFormat) Initialize a new instance of the TextPart class with the specified text format.
Public methodTextPart(String, Object) Initialize a new instance of the TextPart class with the specified text subtype.
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Properties
 NameDescription
Public propertyCode exampleContent Get or set the MIME content.
(Inherited from MimePart)
Public propertyContentBase Get or set the base content URI.
(Inherited from MimeEntity)
Public propertyContentDescription Get or set the description of the content if available.
(Inherited from MimePart)
Public propertyContentDisposition Get or set the content disposition.
(Inherited from MimeEntity)
Public propertyContentDuration Get or set the duration of the content if available.
(Inherited from MimePart)
Public propertyContentId Get or set the Content-Id.
(Inherited from MimeEntity)
Public propertyContentLocation Get or set the content location.
(Inherited from MimeEntity)
Public propertyContentMd5 Get or set the md5sum of the content.
(Inherited from MimePart)
Public propertyContentTransferEncoding Get or set the content transfer encoding.
(Inherited from MimePart)
Public propertyContentType Get the type of the content.
(Inherited from MimeEntity)
Public propertyCode exampleFileName Get or set the name of the file.
(Inherited from MimePart)
Public propertyFormat Get the text format of the content.
Public propertyHeaders Get the list of headers.
(Inherited from MimeEntity)
Public propertyIsAttachment Get a value indicating whether this MimePart is an attachment.
(Inherited from MimeEntity)
Public propertyIsEnriched Get whether or not this text part contains enriched text.
Public propertyCode exampleIsFlowed Get whether or not this text part contains flowed text.
Public propertyCode exampleIsHtml Get whether or not this text part contains HTML.
Public propertyIsPlain Get whether or not this text part contains plain text.
Public propertyIsRichText Get whether or not this text part contains RTF.
Public propertyText Get the decoded text content.
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Methods
 NameDescription
Public methodAccept Dispatches to the specific visit method for this MIME entity.
(Overrides MimePartAccept(MimeVisitor))
Public methodComputeContentMd5 Compute the MD5 checksum of the content.
(Inherited from MimePart)
Public methodDispose Releases all resources used by the MimeEntity object.
(Inherited from MimeEntity)
Protected methodDispose(Boolean) Releases the unmanaged resources used by the MimePart and optionally releases the managed resources.
(Inherited from MimePart)
Public methodEquals
(Inherited from Object)
Protected methodFinalize Releases unmanaged resources and performs other cleanup operations before the MimeEntity is reclaimed by garbage collection.
(Inherited from MimeEntity)
Public methodGetBestEncoding(EncodingConstraint, CancellationToken) Calculate the most efficient content encoding given the specified constraint.
(Inherited from MimePart)
Public methodGetBestEncoding(EncodingConstraint, Int32, CancellationToken) Calculate the most efficient content encoding given the specified constraint.
(Inherited from MimePart)
Public methodGetHashCode
(Inherited from Object)
Public methodGetText(Encoding) Get the decoded text content using the provided charset encoding to override the charset specified in the Content-Type parameters.
Public methodGetText(Encoding) Get the decoded text and the encoding used to convert it into unicode.
Public methodGetText(String) Get the decoded text content using the provided charset to override the charset specified in the Content-Type parameters.
Public methodGetType
(Inherited from Object)
Protected methodMemberwiseClone
(Inherited from Object)
Protected methodOnHeadersChanged Called when the headers change in some way.
(Inherited from MimePart)
Public methodPrepare Prepare the MIME entity for transport using the specified encoding constraints.
(Inherited from MimePart)
Protected methodRemoveHeader Remove a header by name.
(Inherited from MimeEntity)
Protected methodSetHeader(String, Byte) Set the value of a header using the raw value.
(Inherited from MimeEntity)
Protected methodSetHeader(String, String) Set the value of a header.
(Inherited from MimeEntity)
Public methodSetText(Encoding, String) Set the text content and the charset parameter in the Content-Type header.
Public methodSetText(String, String) Set the text content and the charset parameter in the Content-Type header.
Public methodToString Return a String that represents the MimeEntity for debugging purposes.
(Inherited from MimeEntity)
Public methodTryDetectEncoding Try to detect the encoding of the text content.
Protected methodTryInit Tries to use the given object to initialize the appropriate property.
(Inherited from MimeEntity)
Public methodVerifyContentMd5 Verify the Content-Md5 value against an independently computed md5sum.
(Inherited from MimePart)
Public methodWriteTo(Stream, CancellationToken) Write the MimeEntity to the specified output stream.
(Inherited from MimeEntity)
Public methodWriteTo(String, CancellationToken) Write the MimeEntity to the specified file.
(Inherited from MimeEntity)
Public methodWriteTo(FormatOptions, Stream, CancellationToken) Write the MimeEntity to the specified output stream.
(Inherited from MimeEntity)
Public methodWriteTo(FormatOptions, String, CancellationToken) Write the MimeEntity to the specified file.
(Inherited from MimeEntity)
Public methodWriteTo(Stream, Boolean, CancellationToken) Write the MimeEntity to the specified output stream.
(Inherited from MimeEntity)
Public methodWriteTo(String, Boolean, CancellationToken) Write the MimeEntity to the specified file.
(Inherited from MimeEntity)
Public methodWriteTo(FormatOptions, String, Boolean, CancellationToken) Write the MimeEntity to the specified file.
(Inherited from MimeEntity)
Public methodWriteTo(FormatOptions, Stream, Boolean, CancellationToken) Write the MimePart to the specified output stream.
(Inherited from MimePart)
Public methodWriteToAsync(Stream, CancellationToken) Asynchronously write the MimeEntity to the specified output stream.
(Inherited from MimeEntity)
Public methodWriteToAsync(String, CancellationToken) Asynchronously write the MimeEntity to the specified file.
(Inherited from MimeEntity)
Public methodWriteToAsync(FormatOptions, Stream, CancellationToken) Asynchronously write the MimeEntity to the specified output stream.
(Inherited from MimeEntity)
Public methodWriteToAsync(FormatOptions, String, CancellationToken) Asynchronously write the MimeEntity to the specified file.
(Inherited from MimeEntity)
Public methodWriteToAsync(Stream, Boolean, CancellationToken) Asynchronously write the MimeEntity to the specified output stream.
(Inherited from MimeEntity)
Public methodWriteToAsync(String, Boolean, CancellationToken) Asynchronously write the MimeEntity to the specified file.
(Inherited from MimeEntity)
Public methodWriteToAsync(FormatOptions, String, Boolean, CancellationToken) Asynchronously write the MimeEntity to the specified file.
(Inherited from MimeEntity)
Public methodWriteToAsync(FormatOptions, Stream, Boolean, CancellationToken) Asynchronously write the MimePart to the specified output stream.
(Inherited from MimePart)
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Remarks

Unless overridden, all textual parts parsed by the MimeParser, such as text/plain or text/html, will be represented by a TextPart.

For more information about text media types, see section 4.1 of rfc2046.

Example
C#
/// <summary>
/// Visits a MimeMessage and generates HTML suitable to be rendered by a browser control.
/// </summary>
class HtmlPreviewVisitor : MimeVisitor
{
    List<MultipartRelated> stack = new List<MultipartRelated> ();
    List<MimeEntity> attachments = new List<MimeEntity> ();
    string body;

    /// <summary>
    /// Creates a new HtmlPreviewVisitor.
    /// </summary>
    public HtmlPreviewVisitor ()
    {
    }

    /// <summary>
    /// The list of attachments that were in the MimeMessage.
    /// </summary>
    public IList<MimeEntity> Attachments {
        get { return attachments; }
    }

    /// <summary>
    /// The HTML string that can be set on the BrowserControl.
    /// </summary>
    public string HtmlBody {
        get { return body ?? string.Empty; }
    }

    protected override void VisitMultipartAlternative (MultipartAlternative alternative)
    {
        // walk the multipart/alternative children backwards from greatest level of faithfulness to the least faithful
        for (int i = alternative.Count - 1; i >= 0 && body == null; i--)
            alternative[i].Accept (this);
    }

    protected override void VisitMultipartRelated (MultipartRelated related)
    {
        var root = related.Root;

        // push this multipart/related onto our stack
        stack.Add (related);

        // visit the root document
        root.Accept (this);

        // pop this multipart/related off our stack
        stack.RemoveAt (stack.Count - 1);
    }

    // look up the image based on the img src url within our multipart/related stack
    bool TryGetImage (string url, out MimePart image)
    {
        UriKind kind;
        int index;
        Uri uri;

        if (Uri.IsWellFormedUriString (url, UriKind.Absolute))
            kind = UriKind.Absolute;
        else if (Uri.IsWellFormedUriString (url, UriKind.Relative))
            kind = UriKind.Relative;
        else
            kind = UriKind.RelativeOrAbsolute;

        try {
            uri = new Uri (url, kind);
        } catch {
            image = null;
            return false;
        }

        for (int i = stack.Count - 1; i >= 0; i--) {
            if ((index = stack[i].IndexOf (uri)) == -1)
                continue;

            image = stack[i][index] as MimePart;
            return image != null;
        }

        image = null;

        return false;
    }

    /// <summary>
    /// Get a data: URI for the image attachment.
    /// </summary>
    /// <remarks>
    /// Encodes the image attachment into a string suitable for setting as a src= attribute value in
    /// an img tag.
    /// </remarks>
    /// <returns>The data: URI.</returns>
    /// <param name="image">The image attachment.</param>
    string GetDataUri (MimePart image)
    {
        using (var memory = new MemoryStream ()) {
            image.Content.DecodeTo (memory);
            var buffer = memory.GetBuffer ();
            var length = (int) memory.Length;
            var base64 = Convert.ToBase64String (buffer, 0, length);

            return string.Format ("data:{0};base64,{1}", image.ContentType.MimeType, base64);
        }
    }

    // Replaces <img src=...> urls that refer to images embedded within the message with
    // "file://" urls that the browser control will actually be able to load.
    void HtmlTagCallback (HtmlTagContext ctx, HtmlWriter htmlWriter)
    {
        if (ctx.TagId == HtmlTagId.Meta && !ctx.IsEndTag) {
            bool isContentType = false;

            ctx.WriteTag (htmlWriter, false);

            // replace charsets with "utf-8" since our output will be in utf-8 (and not whatever the original charset was)
            foreach (var attribute in ctx.Attributes) {
                if (attribute.Id == HtmlAttributeId.Charset) {
                    htmlWriter.WriteAttributeName (attribute.Name);
                    htmlWriter.WriteAttributeValue ("utf-8");
                } else if (isContentType && attribute.Id == HtmlAttributeId.Content) {
                    htmlWriter.WriteAttributeName (attribute.Name);
                    htmlWriter.WriteAttributeValue ("text/html; charset=utf-8");
                } else {
                    if (attribute.Id == HtmlAttributeId.HttpEquiv && attribute.Value != null
                        && attribute.Value.Equals ("Content-Type", StringComparison.OrdinalIgnoreCase))
                        isContentType = true;

                    htmlWriter.WriteAttribute (attribute);
                }
            }
        } else if (ctx.TagId == HtmlTagId.Image && !ctx.IsEndTag && stack.Count > 0) {
            ctx.WriteTag (htmlWriter, false);

            // replace the src attribute with a "data:" URL
            foreach (var attribute in ctx.Attributes) {
                if (attribute.Id == HtmlAttributeId.Src) {
                    if (!TryGetImage (attribute.Value, out var image)) {
                        htmlWriter.WriteAttribute (attribute);
                        continue;
                    }

                    var dataUri = GetDataUri (image);

                    htmlWriter.WriteAttributeName (attribute.Name);
                    htmlWriter.WriteAttributeValue (dataUri);
                } else {
                    htmlWriter.WriteAttribute (attribute);
                }
            }
        } else if (ctx.TagId == HtmlTagId.Body && !ctx.IsEndTag) {
            ctx.WriteTag (htmlWriter, false);

            // add and/or replace oncontextmenu="return false;"
            foreach (var attribute in ctx.Attributes) {
                if (attribute.Name.Equals ("oncontextmenu", StringComparison.OrdinalIgnoreCase))
                    continue;

                htmlWriter.WriteAttribute (attribute);
            }

            htmlWriter.WriteAttribute ("oncontextmenu", "return false;");
        } else {
            // pass the tag through to the output
            ctx.WriteTag (htmlWriter, true);
        }
    }

    protected override void VisitTextPart (TextPart entity)
    {
        TextConverter converter;

        if (body != null) {
            // since we've already found the body, treat this as an attachment
            attachments.Add (entity);
            return;
        }

        if (entity.IsHtml) {
            converter = new HtmlToHtml {
                HtmlTagCallback = HtmlTagCallback
            };
        } else if (entity.IsFlowed) {
            var flowed = new FlowedToHtml ();
            string delsp;

            if (entity.ContentType.Parameters.TryGetValue ("delsp", out delsp))
                flowed.DeleteSpace = delsp.Equals ("yes", StringComparison.OrdinalIgnoreCase);

            converter = flowed;
        } else {
            converter = new TextToHtml ();
        }

        body = converter.Convert (entity.Text);
    }

    protected override void VisitTnefPart (TnefPart entity)
    {
        // extract any attachments in the MS-TNEF part
        attachments.AddRange (entity.ExtractAttachments ());
    }

    protected override void VisitMessagePart (MessagePart entity)
    {
        // treat message/rfc822 parts as attachments
        attachments.Add (entity);
    }

    protected override void VisitMimePart (MimePart entity)
    {
        // realistically, if we've gotten this far, then we can treat this as an attachment
        // even if the IsAttachment property is false.
        attachments.Add (entity);
    }
}
See Also