Expression examples in Power BI Report Builder

Article
06/16/2023

APPLIES TO: Power BI Report Builder Power BI Desktop

Expressions are used frequently in Power BI Report Builder paginated reports to control content and report appearance. Expressions are written in Microsoft Visual Basic, and can use built-in functions, custom code, report and group variables, and user-defined variables. Expressions begin with an equal sign (=).

This article provides examples of expressions that can be used for common tasks in a report.

Visual Basic functions: Examples for date, string, conversion, and conditional Visual Basic functions.
Report functions: Examples for aggregates and other built-in report functions.
Appearance of report data: Examples for changing the appearance of a report.
Properties: Examples for setting report item properties to control format or visibility.
Parameters: Examples for using parameters in an expression.
Custom code: Examples of embedded custom code.

For more information about simple and complex expressions, where you can use expressions, and the types of references that you can include in an expression, see Expressions in Power BI Report Builder.

Functions

Many expressions in a report contain functions. You can format data, apply logic, and access report metadata using these functions. You can write expressions that use functions from the Microsoft Visual Basic runtime library, and from the xref:System.Convert and xref:System.Math namespaces. You can add references to functions in custom code. You can also use classes from the Microsoft .NET Framework, including xref:System.Text.RegularExpressions.

Visual Basic functions

You can use Visual Basic functions to manipulate the data that's displayed in text boxes or used for parameters, properties, or other areas of the report. This section provides examples demonstrating some of these functions. For more information, see Visual Basic runtime library members on MSDN.

The .NET Framework provides many custom format options, for example, for specific date formats. For more information, see Formatting types.

Math functions

The Round function is useful to round numbers to the nearest integer. The following expression rounds 1.3 to 1:
```
=Round(1.3)  
```
You can also write an expression to round a value to a multiple that you specify, similar to the MRound function in Excel. Multiply the value by a factor that creates an integer, round the number, and then divide by the same factor. For example, to round 1.3 to the nearest multiple of 0.2, which is 1.4, use the following expression:
```
=Round(1.3*5)/5  
```

Date functions

The Today function provides the current date. This expression can be used in a text box to display the date on the report, or in a parameter to filter data based on the current date.
```
=Today()  
```
Use the DateInterval function to pull out a specific part of a date. Here are some valid DateInterval parameters:
- DateInterval.Second
- DateInterval.Minute
- DateInterval.Hour
- DateInterval.Weekday
- DateInterval.Day
- DateInterval.DayOfYear
- DateInterval.WeekOfYear
- DateInterval.Month
- DateInterval.Quarter
- DateInterval.Year
For example, this expression will show the number of the week in the current year for today's date:
```
=DatePart(DateInterval.WeekOfYear, today()) 
```
The DateAdd function is useful for supplying a range of dates based on a single parameter. The following expression provides a date that is six months after the date from a parameter named StartDate.
```
=DateAdd(DateInterval.Month, 6, Parameters!StartDate.Value)  
```
The Year function displays the year for a particular date. You can group dates together or to display the year as a label for a set of dates. This expression provides the year for a given group of sales order dates. The Month function and other functions can also be used to manipulate dates. For more information, see the Visual Basic documentation.
```
=Year(Fields!OrderDate.Value)  
```
You can combine functions in an expression to customize the format. The following expression changes the format of a date in the form month-day-year to month-week-week number. For example, change "12/18/2022" to "December Week 3":
```
=Format(Fields!MyDate.Value, "MMMM") & " Week " &   
(Int(DateDiff("d", DateSerial(Year(Fields!MyDate.Value),   
Month(Fields!MyDate.Value),1), Fields!FullDateAlternateKey.Value)/7)+1).ToString  
```
When used as a calculated field in a dataset, you can use this expression on a chart to aggregate values by week within each month.
The following expression formats the SellStartDate value as MMM-yy. The SellStartDate field is a datetime data type.
```
=FORMAT(Fields!SellStartDate.Value, "MMM-yy")  
```
The following expression formats the SellStartDate value as dd/MM/yyyy. The SellStartDate field is a datetime data type.
```
=FORMAT(Fields!SellStartDate.Value, "dd/MM/yyyy")  
```
The CDate function converts the value to a date. The Now function returns a date value containing the current date and time according to your system. DateDiff returns a Long value specifying the number of time intervals between two Date values.

The following example displays the start date of the current year
```
=DateAdd(DateInterval.Year,DateDiff(DateInterval.Year,CDate("01/01/1900"),Now()),CDate("01/01/1900"))  
```

The following example displays the start date for the previous month based on the current month.

=DateAdd(DateInterval.Month,DateDiff(DateInterval.Month,CDate("01/01/1900"),Now())-1,CDate("01/01/1900"))

The following expression generates the interval years between SellStartDate and LastReceiptDate. These fields are in two different datasets, DataSet1 and DataSet2.
```
=DATEDIFF("yyyy", First(Fields!SellStartDate.Value, "DataSet1"), First(Fields!LastReceiptDate.Value, "DataSet2"))  
```
The DatePart function returns an Integer value containing the specified component of a given Date value. The following expression returns the year for the first value of the SellStartDate in DataSet1. The dataset scope is specified because there are multiple datasets in the report.
```
=Datepart("yyyy", First(Fields!SellStartDate.Value, "DataSet1"))  
```
The DateSerial function returns a Date value representing a specified year, month, and day, with the time information set to midnight. The following example displays the ending date for the prior month, based on the current month.
```
=DateSerial(Year(Now()), Month(Now()), "1").AddDays(-1)  
```
The following expressions display various dates based on a date parameter value selected by the user.

Example description	Example
Yesterday	`=DateSerial(Year(Parameters!TodaysDate.Value),Month(Parameters!TodaysDate.Value),Day(Parameters!TodaysDate.Value)-1)`
Two days ago	`=DateSerial(Year(Parameters!TodaysDate.Value),Month(Parameters!TodaysDate.Value),Day(Parameters!TodaysDate.Value)-2)`
One month ago	`=DateSerial(Year(Parameters!TodaysDate.Value),Month(Parameters!TodaysDate.Value)-1,Day(Parameters!TodaysDate.Value))`
Two months ago	`=DateSerial(Year(Parameters!TodaysDate.Value),Month(Parameters!TodaysDate.Value)-2,Day(Parameters!TodaysDate.Value))`
One year ago	`=DateSerial(Year(Parameters!TodaysDate.Value)-1,Month(Parameters!TodaysDate.Value),Day(Parameters!TodaysDate.Value))`
Two years ago	`=DateSerial(Year(Parameters!TodaysDate.Value)-2,Month(Parameters!TodaysDate.Value),Day(Parameters!TodaysDate.Value))`

String functions

Combine more than one field by using concatenation operators and Visual Basic constants. The following expression returns two fields, each on a separate line in the same text box:
```
=Fields!FirstName.Value & vbCrLf & Fields!LastName.Value   
```
Format dates and numbers in a string with the Format function. The following expression displays values of the StartDate and EndDate parameters in long date format:
```
=Format(Parameters!StartDate.Value, "D") & " through " &  Format(Parameters!EndDate.Value, "D")    
```
If the text box contains only a date or number, you should use the Format property of the text box to apply formatting instead of the Format function within the text box.
The Right, Len, and InStr functions are useful for returning a substring, for example, trimming DOMAIN\username to just the user name. The following expression returns the part of the string to the right of a backslash (\) character from a parameter named User:
```
=Right(Parameters!User.Value, Len(Parameters!User.Value) - InStr(Parameters!User.Value, "\"))  
```
The following expression results in the same value as the previous one, using members of the .NET Framework xref:System.String class instead of Visual Basic functions:
```
=Parameters!User.Value.Substring(Parameters!User.Value.IndexOf("\")+1, Parameters!User.Value.Length-Parameters!User.Value.IndexOf("\")-1)  
```
Display the selected values from a multivalue parameter. The following example uses the Join function to concatenate the selected values of the parameter MySelection into a single string that can be set as an expression for the value of a text box in a report item:
```
= Join(Parameters!MySelection.Value)  
```
The following example does the same as the previous example, and displays a text string prior to the list of selected values.
```
="Report for " & JOIN(Parameters!MySelection.Value, " & ")  
```
The Regex functions from the .NET Framework xref:System.Text.RegularExpressions are useful for changing the format of existing strings, for example, formatting a telephone number. The following expression uses the Replace function to change the format of a ten-digit telephone number in a field from "nnn-nnn-nnnn" to "(nnn) nnn-nnnn":
```
=System.Text.RegularExpressions.Regex.Replace(Fields!Phone.Value, "(\d{3})[ -.]*(\d{3})[ -.]*(\d{4})", "($1) $2-$3")  
```
Note

Verify that the value for Fields!Phone.Value has no extra spaces and is of type xref:System.String.

Lookup

By specifying a key field, you can use the Lookup function to retrieve a value from a dataset for a one-to-one relationship, for example, a key-value pair. The following expression displays the product name from a dataset ("Product"), given the product identifier to match on:
```
=Lookup(Fields!PID.Value, Fields!ProductID.Value, Fields.ProductName.Value, "Product")  
```

LookupSet

By specifying a key field, you can use the LookupSet function to retrieve a set of values from a dataset for a one-to-many relationship. For example, a person can have multiple telephone numbers. In the following example, assume the dataset PhoneList contains a person identifier and a telephone number in each row. LookupSet returns an array of values. The following expression combines the return values into a single string and displays the list of telephone numbers for the person specified by ContactID:
```
=Join(LookupSet(Fields!ContactID.Value, Fields!PersonID.Value, Fields!PhoneNumber.Value, "PhoneList"),",")  
```

Conversion functions

You can use Visual Basic functions to convert a field from the one data type to a different data type. Conversion functions can be used to convert the default data type for a field to the data type needed for calculations or to combine text.

The following expression converts the constant 500 to type Decimal in order to compare it to a Transact-SQL money data type in the Value field for a filter expression.
```
=CDec(500)  
```
The following expression displays the number of values selected for the multivalue parameter MySelection.
```
=CStr(Parameters!MySelection.Count)  
```

Decision functions

The IIF function returns one of two values depending on whether the expression is true or not. The following expression uses the IIF function to return a Boolean value of True if the value of LineTotal exceeds 100. Otherwise it returns False:
```
=IIF(Fields!LineTotal.Value > 100, True, False)  
```
Use multiple IIF functions (also known as "nested IIFs") to return one of three values depending on the value of PctComplete. The following expression can be placed in the fill color of a text box to change the background color depending on the value in the text box.
```
=IIF(Fields!PctComplete.Value >= 10, "Green", IIF(Fields!PctComplete.Value >= 1, "Blue", "Red"))  
```
Values greater than or equal to 10 display with a green background, between 1 and 9 display with a blue background, and less than 1 display with a red background.
A different way to get the same functionality uses the Switch function. The Switch function is useful when there are three or more conditions to test. The Switch function returns the value associated with the first expression in a series that evaluates to true:
```
=Switch(Fields!PctComplete.Value >= 10, "Green", Fields!PctComplete.Value >= 1, "Blue", Fields!PctComplete.Value = 1, "Yellow", Fields!PctComplete.Value <= 0, "Red")  
```
Values greater than or equal to 10 display with a green background, between 1 and 9 display with a blue background, equal to 1 display with a yellow background, and 0 or less display with a red background.
Test the value of the ImportantDate field and return "Red" if it's more than a week old, and "Blue" otherwise. This expression can be used to control the Color property of a text box in a report item:
```
=IIF(DateDiff("d",Fields!ImportantDate.Value, Now())>7,"Red","Blue")  
```
Test the value of the PhoneNumber field and return "No Value" if it's null (Nothing in Visual Basic); otherwise return the phone number value. This expression can be used to control the value of a text box in a report item.
```
=IIF(Fields!PhoneNumber.Value Is Nothing,"No Value",Fields!PhoneNumber.Value)  
```
Test the value of the Department field and return either a subreport name or a null (Nothing in Visual Basic). This expression can be used for conditional drillthrough subreports.
```
=IIF(Fields!Department.Value = "Development", "EmployeeReport", Nothing)  
```
Test if a field value is null. This expression can be used to control the Hidden property of an image report item. In the following example, the image specified by the field LargePhoto is displayed only if the value of the field isn't null.
```
=IIF(IsNothing(Fields!LargePhoto.Value),True,False)  
```
The MonthName function returns a string value containing the name of the specified month. The following example displays NA in the Month field when the field contains the value of 0.
```
IIF(Fields!Month.Value=0,"NA",MonthName(IIF(Fields!Month.Value=0,1,Fields!Month.Value)))  
```

Report functions

In an expression, you can add a reference to additional report functions that manipulate data in a report. This section provides examples for two of these functions.

Sum

The Sum function can total the values in a group or data region. This function can be useful in the header or footer of a group. The following expression displays the sum of data in the Order group or data region:
```
=Sum(Fields!LineTotal.Value, "Order")  
```
You can also use the Sum function for conditional aggregate calculations. For example, if a dataset has a field that is named State with possible values Not Started, Started, Finished, the following expression, when placed in a group header, calculates the aggregate sum for only the value Finished:
```
=Sum(IIF(Fields!State.Value = "Finished", 1, 0))  
```

RowNumber

The RowNumber function, when used in a text box within a data region, displays the row number for each instance of the text box in which the expression appears. This function can be useful to number rows in a table. It can also be useful for more complex tasks, such as providing page breaks based on the number of rows. For more information, see Page breaks in this article.

The scope you specify for RowNumber controls when renumbering begins. The Nothing keyword indicates that the function will start counting at the first row in the outermost data region. To start counting within nested data regions, use the name of the data region. To start counting within a group, use the name of the group.
```
=RowNumber(Nothing)  
```

Appearance of report data

You can use expressions to manipulate how data appears on a report. For example, you can display the values of two fields in a single text box, display information about the report, or affect how page breaks are inserted in the report.

Page headers and footers

When designing a report, you can 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:
```
=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:
```
=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:
```
=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:
```
=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:
```
=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.

Page breaks

In some reports, you can place a page break at the end of a specified number of rows instead of, or in addition to, on groups or report items. 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.
```
=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:
```
=Ceiling(RowNumber(Nothing)/Parameters!RowsPerPage.Value)  
```

Properties

Expressions aren't only used to display data in text boxes. They can also be used to change how properties are applied to report items. You can change style information for a report item, or change its visibility.

Formatting

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:
```
=Iif(Fields!Profit.Value < 0, "Red", "Black")  
```
You can also use the Visual Basic object variable Me. This variable is another way of referring to the value of a text box.

=Iif(Me.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:
```
=Iif(RowNumber(Nothing) Mod 2, "PaleGreen", "White")  
```
If you use an expression for a specified scope, you might have to indicate the dataset for the aggregate function:
```
=Iif(RowNumber("Employees") Mod 2, "PaleGreen", "White")  
```

Note

Available colors come from the .NET Framework KnownColor enumeration.

Chart colors

To specify colors for a Shape chart, you can use custom code to control the order that colors are mapped to data point values. This helps you use consistent colors for multiple charts that have the same category groups.

Visibility

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:
```
=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:
```
=IIF(CountRows()>12,false,true)  
```
The following expression, when set in the Hidden property of a column, shows the column only if the field exists in the report dataset after the data is retrieved from the data source:
```
=IIF(Fields!Column_1.IsMissing, true, false)  
```

URLs

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.
```
="https://adventure-works/MyInfo?ID=" & Fields!EmployeeID.Value  
```
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 to Microsoft Excel without hyperlinks.
```
=IIF(Parameters!IncludeURLs.Value,"https://adventure-works.com/productcatalog",Nothing)  
```

Note

Power BI paginated reports don't support using JavaScript within a Go To URL expression.

Report data

Expressions can be used to manipulate the data that is used in the report. You can refer to parameters and other report information. You can even change the query that is used to retrieve data for the report.

Parameters

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:
```
=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:
```
=Parameters!Department.Value  
```
Parameters can be created in a report but set to hidden. When the report runs on the report server, the parameter doesn't appear in the toolbar and the report reader can't change the default value. You can use a hidden parameter set to a default value a 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:
```
=Fields(Parameters!ParameterField.Value).Value  
```

Custom code

You can use custom code embedded in a report.

Using group variables for custom aggregation

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.

Suppressing null or zero values at run time

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.
```
=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's no previous value) and cases where either the previous value or the current value is null (Nothing in Visual Basic).
```
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, for the ColumnGroupByYear container (group or data region).
```
=Code.GetDeltaPercentage(Previous(Sum(Fields!Sales.Value),"ColumnGroupByYear"), Sum(Fields!Sales.Value))  
```
This code helps to avoid run-time exceptions. You can now use an expression like =IIF(Me.Value < 0, "red", "black") in the Color property of the text box to conditionally display text based on whether the values are greater than or less than 0.

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Expression examples in Power BI Report Builder

Functions

Visual Basic functions

Math functions

Date functions

String functions

Lookup

LookupSet

Conversion functions

Decision functions

Report functions

Sum

RowNumber

Appearance of report data

Page headers and footers

Page breaks

Properties

Formatting

Chart colors

Visibility

URLs

Report data

Parameters

Custom code

Using group variables for custom aggregation

Suppressing null or zero values at run time

Next steps

Feedback

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