(转载)SQL Reporting Services (Expression Examples)

You can use Visual Basic functions to manipulate the data that is displayed in text boxes or that is used for parameters, properties, or other areas of the report. This section provides examples that demonstrate some of these functions. These examples specify Visual Basic constants as enumeration values, for example, DateInterval.Month. Although the expression editor does not support Intellisense for these values, they compile correctly in an expression.

For more information about Visual Basic functions, see the Visual Basic documentation.

Date Functions

String Functions

Conversion Functions

Decision Functions

Reporting Services provides additional report functions that you can use to manipulate data in a report. This section provides examples for two of these functions. For more information about report functions and examples, see Using Built-in Report and Aggregate Functions in Expressions (Reporting Services).

When designing a report, you may want to display the name of the report and page number in the report footer. To do this, you can use the following expressions: 

• The following expression provides the name of the report and the time it was run. It can be placed in a text box in the report footer or in the body of the report. The time is formatted with the .NET Framework formatting string for short date:

   

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  =Globals.ReportName & ", dated " & Format(Globals.ExecutionTime, "d")
  

• The following expression, placed in a text box in the footer of a report, provides page number and total pages in the report:

   

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  =Globals.PageNumber & " of " & Globals.TotalPages
  

The following examples describe how to display the first and last values from a page in the page header, similar to what you might find in a directory listing. The example assumes a data region that contains a text box named LastName. 

• The following expression, placed in a text box on the left side of the page header, provides the first value of the LastName text box on the page:

   

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  =First(ReportItems("LastName").Value)
  

• The following expression, placed in a text box on the right side of the page header, provides the last value of the LastName text box on the page:

   

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  =Last(ReportItems("LastName").Value)
  

The following example describes how to display a page total. The example assumes a data region that contains a text box named Cost. 

• The following expression, placed in the page header or footer, provides the sum of the values in the Cost text box for the page:

   

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  =Sum(ReportItems("Cost").Value)
  

Note
You can refer to only one report item per expression in a page header or footer. Also, you can refer to the text box name, but not the actual data expression within the text box, in page header and footer expressions.

In some reports, you may want to place a page break at the end of a specified number of rows instead of, or in addition to, on groups or report items. To do this, create a group that contains the groups or detail records you want, add a page break to the group, and then add a group expression to group by a specified number of rows. 

• The following expression, when placed in the group expression, assigns a number to each set of 25 rows. When a page break is defined for the group, this expression results in a page break every 25 rows.

   

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  =CInt(Ceiling(RowNumber(Nothing)/25))
  

  To allow the user to set a value for the number of rows per page, create a parameter named RowsPerPage and base the group expression on the parameter, as shown in the following expression:

   

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  =CInt(Ceiling(RowNumber(Nothing)/Parameters!RowsPerPage.Value))
  

  For more information about setting page breaks for a group, see How to: Add a Page Break (Reporting Services).

• The following expression, when used in the Color property of a text box, changes the color of the text depending on the value of the Profit field:

   

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  =Iif(Fields!Profit.Value < 0, "Red", "Black")
  

• The following expression, when used in the BackgroundColor property of a report item in a data region, alternates the background color of each row between pale green and white:

   

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  =Iif(RowNumber(Nothing) Mod 2, "PaleGreen", "White")
  

  If you are using an expression for a specified scope, you may have to indicate the dataset for the aggregate function:

   

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  =Iif(RowNumber("Employees") Mod 2, "PaleGreen", "White")
  

Note
Available colors come from the .NET FrameworkKnownColor enumeration.

You can show and hide items in a report using the visibility properties for the report item. In a data region such as a table, you can initially hide detail rows based on the value in an expression. 

• The following expression, when used for initial visibility of detail rows in a group, shows the detail rows for all sales exceeding 90 percent in the PctQuota field:

   

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  =Iif(Fields!PctQuota.Value>.9, False, True)
  

• The following expression, when set in the Hidden property of a table, shows the table only if it has more than 12 rows:

   

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  =IIF(CountRows()>12,true,false)
  

You can customize URLs by using report data and also conditionally control whether URLs are added as an action for a text box.

• The following expression, when used as an action on a text box, generates a customized URL that specifies the dataset field EmployeeID as a URL parameter.

   

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  ="http://adventure-works/MyInfo?ID=" & Fields!EmployeeID.Value
  

  For more information, see How to: Add a Hyperlink to a URL (Reporting Services).

• The following expression conditionally controls whether to add a URL in a text box. This expression depends on a parameter named IncludeURLs that allows a user to decide whether to include active URLs in a report. This expression is set as an action on a text box. By setting the parameter to False and then viewing the report, you can export the report Microsoft Excel without hyperlinks.

   

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  =IIF(Parameters!IncludeURLs.Value,"http://adventure-works.com/productcatalog",Nothing)
  

You can use expressions in a parameter to vary the default value for the parameter. For example, you can use a parameter to filter data to a particular user based on the user ID that is used to run the report. 

• The following expression, when used as the default value for a parameter, collects the user ID of the person running the report:

   

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  =User!UserID
  

• To refer to a parameter in a query parameter, filter expression, text box, or other area of the report, use the Parameters global collection. This example assumes that the parameter is named Department:

   

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  =Parameters!Department.Value
  

• Parameters can be created in a report but set to hidden. When the report runs on the report server, the parameter does not appear in the toolbar and the report reader cannot change the default value. You can use a hidden parameter set to a default value as custom constant. You can use this value in any expression, including a field expression. The following expression identifies the field specified by the default parameter value for the parameter named ParameterField:

   

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  =Fields(Parameters!ParameterField.Value).Value
  

  For more information, see Setting Parameter Properties for a Published Report.

You can initialize the value for a group variable that is local to a particular group scope and then include a reference to that variable in expressions. One of the ways that you can use a group variable with custom code is to implement a custom aggregate. For more information, see Using Group Variables in Reporting Services 2008 for Custom Aggregation.

For more information about variables, see Using Report and Group Variables Collection References in Expressions (Reporting Services).

The following example calls an embedded method called FixSpelling, which substitutes "Bicycle" for all occurrences of the text "Bike" in SubCategory.Value.

=Code.FixSpelling(Fields!SubCategory.Value)

The following code, when embedded in a report definition, shows an implementation of the FixSpelling method. This example shows you how to refer to the .NET Framework System.Text.StringBuilder class. For more information, see How to: Add Code to a Report (Reporting Services) and How to: Add an Assembly Reference to a Report (Reporting Services).

Public Function FixSpelling(ByVal s As String) As String
   Dim strBuilder As New System.Text.StringBuilder(s)
   If s.Contains("Bike") Then
      strBuilder.Replace("Bike", "Bicycle")
      Return strBuilder.ToString()
      Else : Return s
   End If
End Function

Some values in an expression can evaluate to null or undefined at report processing time. This can create run-time errors that result in #Error displaying in the text box instead of the evaluated expression. The IIF function is particularly sensitive to this behavior because, unlike an If-Then-Else statement, each part of the IIF statement is evaluated (including function calls) before being passed to the routine that tests for true or false. The statement =IIF(Fields!Sales.Value is NOTHING, 0, Fields!Sales.Value) generates #Error in the rendered report if Fields!Sales.Value is NOTHING.

To avoid this condition, use one of the following strategies:

• Set the numerator to 0 and the denominator to 1 if the value for field B is 0 or undefined; otherwise, set the numerator to the value for field A and the denominator to the value for field B.

   

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  =IIF(Field!B.Value=0, 0, Field!A.Value / IIF(Field!B.Value =0, 1, Field!B.Value))
  

• Use a custom code function to return the value for the expression. The following example returns the percentage difference between a current value and a previous value. This can be used to calculate the difference between any two successive values and it handles the edge case of the first comparison (when there is no previous value) and cases whether either the previous value or the current value is null (Nothing in Visual Basic).

   

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  Public Function GetDeltaPercentage(ByVal PreviousValue, ByVal CurrentValue) As Object
      If IsNothing(PreviousValue) OR IsNothing(CurrentValue) Then
          Return Nothing
      Else if PreviousValue = 0 OR CurrentValue = 0 Then
          Return Nothing
      Else 
          Return (CurrentValue - PreviousValue) / CurrentValue
      End If
  End Function
  

  The following expression shows how to call this custom code from a text box:

   

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  =Code.GetDeltaPercentage(Previous(Sum(Fields!Sales.Value),"ColumnGroupByYear"), Sum(Fields!Sales.Value))