public string CriteriaString { get; set; }

Public Property CriteriaString As String

using DevExpress.ExpressApp;
using DevExpress.ExpressApp.ReportsV2.Win;
using DevExpress.Persistent.Base.ReportsV2;
// ...
public sealed partial class MySolutionWindowsFormsModule : ModuleBase {
    // ...
    public MySolutionWindowsFormsModule() {
        InitializeComponent();
        ReportsWindowsFormsModuleV2.CreateCustomReportDesignRepositoryItem += 
        ReportsWindowsFormsModuleV2_CreateCustomReportDesignRepositoryItem;
    }
    private void ReportsWindowsFormsModuleV2_CreateCustomReportDesignRepositoryItem(object sender, 
    CreateCustomReportDesignRepositoryItemEventArgs e) {
        e.CriteriaString = "[MyProperty] = True";
    }
}