The sizeInfo property cannot be used with a string field since the minDataValue and maxDataValue need to be numbers. When used with a numeric field, this property works. Example application showing the property working: https://jsfiddle.net/lboyd/unv64swe/9/
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var json = {
"labelExpressionInfo": {
"value": "{POP2007}"
},
};
//create instance of LabelClass (note: multiple LabelClasses can be passed in as an array)
var labelClass = new LabelClass(json);
labelClass.symbol = statesLabel; // symbol also can be set in LabelClass' json
labelClass.sizeInfo = {
"field": "POP2007",
"minSize": 10,
"maxSize": 20,
"minDataValue": 1993495,
"maxDataValue": 37483448
};
states.setLabelingInfo([labelClass]);
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