To perform data binding in report parameters, the steps are as follows:   

1. Run FlexReportDesigner.exe application.
2. Create a new report. Bind it to a data source, which is the Main data source. The report opens in the Design mode.
3. Click the Data tab.
4. Right-click Data Sources and select Add Data Source The Data Sources dialog box appears.
       
5. Select a Data Source, say DataSource1, to create a new data source and set Connection, Data provider, Connection string, etc.
6. You can rename DataSource1 from the Properties window by setting Name property. In our case, we have set Name to dsCategories.
7. Add a parameter by right-clicking Parameters and then selecting Add Parameter.
8. From the Properties window, click the ellipsis button next to AllowedValuesDefinition. The AllowedValuesDefinition Editor dialog box appears.
       
9. Select the From Data Source radio button and then select Data Source, Label, and Value for binding the data source to the parameter as shown. Click OK.
10. From the Properties window, set the DataType to a value that is same as the data type of Value in the AllowedValuesDefinition Editor. In our case, DataType is set to Integer since Value=CategoryID is integer.