public static IEnumerable<IDataSourceAssignable> GetDataSourceAssignables(
    XtraReport report,
    bool includeSubReports = false
)

Public Shared Function GetDataSourceAssignables(
    report As XtraReport,
    includeSubReports As Boolean = False
) As IEnumerable(Of IDataSourceAssignable)

using DevExpress.DataAccess.Json;
using DevExpress.XtraReports.UI;
using DevExpress.XtraReports;
//...

var report = new XtraReport1();

var dataSourceAssignables = DataSourceManager.GetDataSourceAssignables(
    report,
    includeSubReports: true
);

var jsonDataSource = new JsonDataSource() { /* ... */ };

foreach (var elem in dataSourceAssignables) {
    if (elem is XRChart) {
        DataSourceManager.ReplaceDataSource(report, elem.DataSource, jsonDataSource);
    }
}

Imports DevExpress.DataAccess.Json
Imports DevExpress.XtraReports.UI
Imports DevExpress.XtraReports
'...

Private report = New XtraReport1()

Private dataSourceAssignables = DataSourceManager.GetDataSourceAssignables(report, includeSubReports:= True)

Private jsonDataSource = New JsonDataSource()

For Each elem In dataSourceAssignables
    If TypeOf elem Is XRChart Then
        DataSourceManager.ReplaceDataSource(report, elem.DataSource, jsonDataSource)
    End If
Next elem