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OnProcessRequest

Invoked to processing a TWAIN operations (Triplets).

Syntax

protected virtual TwRC OnProcessRequest(TwDG dg, TwDAT dat, TwMSG msg, IntPtr data)

Parameters

• dg: The Data Group of the operation triplet. Currently, only DG_CONTROL, DG_IMAGE, and DG_AUDIO are defined.
• dat: The Data Argument Type of the operation triplet.
• msg: The Message of the operation triplet.
• data: parameter is a pointer to the data (a variable or, more typically, a structure) that will be used according to the action specified by the operation triplet.

Return Value

TWAIN Return Codes.

Examples

protected override TwRC OnProcessRequest(TwDG dg, TwDAT dat, TwMSG msg, IntPtr data) {
    if(dg==TwDG.Image) {
        switch(dat) {
            case TwDAT.ImageLayout:
                return this._ImageLayoutProcessRequest(msg, data);
            case TwDAT.ImageInfo:
                if((this.State&DataSourceState.Ready)!=0) {
                    return this._ImageInfoProcessRequest(msg, data);
                }
                throw new DataSourceException(TwRC.Failure, TwCC.SeqError);
            case TwDAT.ImageNativeXfer:
                if((this.State&DataSourceState.Ready)!=0) {
                    return this._ImageNativeXferProcessRequest(msg, data);
                }
                throw new DataSourceException(TwRC.Failure, TwCC.SeqError);
            case TwDAT.ImageMemXfer:
                if((this.State&DataSourceState.Ready)!=0) {
                    return this._ImageMemXferProcessRequest(msg, data, false);
                }
                throw new DataSourceException(TwRC.Failure, TwCC.SeqError);
            case TwDAT.ImageMemFileXfer:
                if((this.State&DataSourceState.Ready)!=0) {
                    return this._ImageMemXferProcessRequest(msg, data, true);
                }
                throw new DataSourceException(TwRC.Failure, TwCC.SeqError);
            case TwDAT.ImageFileXfer:
                if((this.State&DataSourceState.Ready)!=0) {
                    return this._ImageFileXferProcessRequest(msg);
                }
                throw new DataSourceException(TwRC.Failure, TwCC.SeqError);
        }
    }
    return base.OnProcessRequest(dg, dat, msg, data);
}