You should assign the title to a temp variable first and then use it.
var title = m_listSensors[(int)@deviceIndex].Location;
<RadzenLineSeries Smooth="true"
Data=@sensorTypeData.Data?[ @deviceIndex ]
Title=@title CategoryProperty="Date" ValueProperty="Value" Stroke="@GetLineColour( @sensorTypeData.SensorTypeName, @deviceIndex)" LineType=@GetLineType(deviceIndex)>
Here is why this happens: Loop variables used in components not working? - #5 by korchev