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Using an External Dataset with Reporting Services

The DataSet object is central to supporting disconnected, distributed data scenarios with ADO.NET. The DataSet object is a memory-resident representation of data that provides a consistent relational programming model regardless of the data source. It can be used with multiple different data sources, with XML data, or to manage data local to the application. The DataSet object represents a complete set of data, including related tables, constraints, and relationships among the tables. Because of the DataSet object's versatility in storing and exposing data, your data may often be processed and transformed into a DataSet object before any reporting on that data occurs.

With Reporting Services data processing extensions, you can integrate any custom DataSet objects that are created by external applications. To accomplish this, you create a custom data processing extension in Reporting Services that acts like a bridge between your DataSet object and the report server. Most of the code for processing this DataSet object is contained in the DataReader class that you create.

The first step in exposing your DataSet object to the report server is to implement a provider specific method in your DataReader class that can populate a DataSet object. The following example shows how to load static data into a DataSet object by using a provider-specific method in your DataReader class.

// Private members of the DataReader class
private System.Data.DataSet m_dataSet;
private int m_currentRow;

// Method to create a dataset
internal void CreateDataSet()
{
   // Create a dataset.
   System.Data.DataSet ds = new System.Data.DataSet("myDataSet");
   // Create a data table. 
   System.Data.DataTable dt = new System.Data.DataTable("myTable");
   // Create a data column and set various properties. 
   System.Data.DataColumn dc = new System.Data.DataColumn(); 
   dc.DataType = System.Type.GetType("System.Decimal"); 
   dc.AllowDBNull = false; 
   dc.Caption = "Number"; 
   dc.ColumnName = "Number"; 
   dc.DefaultValue = 25; 
   // Add the column to the table. 
   dt.Columns.Add(dc); 
   // Add 10 rows and set values. 
   System.Data.DataRow dr; 
   for(int i = 0; i < 10; i++)
   { 
      dr = dt.NewRow(); 
      dr["Number"] = i + 1; 
      // Be sure to add the new row to the DataRowCollection. 
      dt.Rows.Add(dr);
   }

   // Fill the dataset.
   ds.Tables.Add(dt);

   // Use a private variable to store the dataset in your
   // DataReader.
   m_dataSet = ds;

   // Set the current row to -1.
   m_currentRow = -1;
}
public bool Read()
{
   m_currentRow++;
   if (m_currentRow >= m_dataSet.Tables[0].Rows.Count) 
   {
      return (false);
   } 
   else 
   {
      return (true);
   }
}

public int FieldCount
{
   // Return the count of the number of columns, which in
   // this case is the size of the column metadata
   // array.
   get { return m_dataSet.Tables[0].Columns.Count; }
}

public string GetName(int i)
{
   return m_dataSet.Tables[0].Columns[i].ColumnName;
}

public Type GetFieldType(int i)
{
   // Return the actual Type class for the data type.
   return m_dataSet.Tables[0].Columns[i].DataType;
}

public Object GetValue(int i)
{
   return m_dataSet.Tables[0].Rows[m_currentRow][i];
}

public int GetOrdinal(string name)
{
   // Look for the ordinal of the column with the same name and return it.
   // Returns -1 if not found.
   return m_dataSet.Tables[0].Columns[name].Ordinal;
}

Once you create or retrieve your dataset, you can use the DataSet object in your implementations of the Read, GetValue, GetName, GetOrdinal, GetFieldType, and FieldCount members of the DataReader class.

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