创建自定义报表项运行时组件

定义和实例对象

实现自定义报表项之前，必须了解“定义对象”和“实例对象”之间的差别。定义对象用于提供自定义报表项的 RDL 表示形式，而实例对象是定义对象的已计算版本。对于报表上的每一项，都只有一个定义对象。访问包含表达式的定义对象上的属性时，将获取未经计算的表达式字符串。实例对象包含定义对象的已计算版本，与项的定义对象可以是一对多的关系。例如，如果报表有一个 Tablix 数据区域，其详细信息行包含 CustomReportItem，则在此数据区域中，将只有一个定义对象，但是每一行中都有一个实例对象。

实现 ICustomReportItem 接口

若要创建 CustomReportItem 运行时组件，则需要实现 Microsoft.ReportingServices.ProcessingCore.dll 中定义的 ICustomReportItem 接口：

namespace Microsoft.ReportingServices.OnDemandReportRendering
{
    public interface ICustomReportItem
    {
        void GenerateReportItemDefinition(CustomReportItem customReportItem);
void EvaluateReportItemInstance(CustomReportItem customReportItem);
    }
}

实现 ICustomReportItem 接口后，将为您生成两个方法存根：GenerateReportItemDefinition 和 EvaluateReportItemInstance。先调用的是 GenerateReportItemDefinition 方法，该方法用于设置定义属性和创建 Image 对象，后者将包含用于呈现相应项的定义属性和实例属性。EvaluateReportItemInstance 方法在定义对象被计算后调用，该方法可提供将用于呈现相应项的实例对象。

以下示例是用于将相应控件名称呈现为图像的自定义报表项的实现示例。

namespace Microsoft.Samples.ReportingServices
{
    using System;
    using System.Collections.Generic;
    using System.Collections.Specialized;
    using System.Drawing.Imaging;
    using System.IO;
    using System.Text;
    using Microsoft.ReportingServices.OnDemandReportRendering;

    public class PolygonsCustomReportItem : ICustomReportItem
    {
        #region ICustomReportItem Members

        public void GenerateReportItemDefinition(CustomReportItem cri)
        {
            // Create the Image object that will be 
            // used to render the custom report item
            cri.CreateCriImageDefinition();
            Image polygonImage = (Image)cri.GeneratedReportItem;
        }

        public void EvaluateReportItemInstance(CustomReportItem cri)
        {
            // Get the Image definition
            Image polygonImage = (Image)cri.GeneratedReportItem;

            // Create the image for the custom report item
            polygonImage.ImageInstance.ImageData = DrawImage(cri);
        }

        #endregion

        /// <summary>
        /// Creates an image of the CustomReportItem's name
        /// </summary>
        private byte[] DrawImage(CustomReportItem customReportItem)
        {
            int width = 1;          // pixels
            int height = 1;         // pixels
            int resolution = 75;    // dpi

            System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(width, height);
            bitmap.SetResolution(resolution, resolution);

            System.Drawing.Graphics graphics = System.Drawing.Graphics.FromImage(bitmap);
            graphics.PageUnit = System.Drawing.GraphicsUnit.Pixel;

            // Get the Font for the Text
            System.Drawing.Font font = new System.Drawing.Font(System.Drawing.FontFamily.GenericMonospace,
                12, System.Drawing.FontStyle.Regular);

            // Get the Brush for drawing the Text
            System.Drawing.Brush brush = new System.Drawing.SolidBrush(System.Drawing.Color.LightGreen);

            // Get the measurements for the image
            System.Drawing.SizeF maxStringSize = graphics.MeasureString(customReportItem.Name, font);
            width = (int)(maxStringSize.Width + 2 * font.GetHeight(resolution));
            height = (int)(maxStringSize.Height + 2 * font.GetHeight(resolution));

            bitmap.Dispose();
            bitmap = new System.Drawing.Bitmap(width, height);
            bitmap.SetResolution(resolution, resolution);

            graphics.Dispose();
            graphics = System.Drawing.Graphics.FromImage(bitmap);
            graphics.PageUnit = System.Drawing.GraphicsUnit.Pixel;
            
            // Draw the text
            graphics.DrawString(customReportItem.Name, font, brush, font.GetHeight(resolution), 
                font.GetHeight(resolution));

            // Create the byte array of the image data
            MemoryStream memoryStream = new MemoryStream();
            bitmap.Save(memoryStream, ImageFormat.Bmp);
            memoryStream.Position = 0;
            byte[] imageData = new byte[memoryStream.Length];
            memoryStream.Read(imageData, 0, imageData.Length);

            return imageData;
        }
    }
}

请参阅

任务

概念