Code SnippetSolidWorks API2026-03-13

Read & Write SolidWorks Custom Properties

Access and modify custom properties on SolidWorks documents and configurations using the CustomPropertyManager. The foundation of every SolidWorks automation project.

csharp

public void ReadWriteCustomProperties(ModelDoc2 model)
{
    var ext = model.Extension;

    // Read all file-level custom properties
    var mgr = ext.CustomPropertyManager[""];
    object names = null, types = null, values = null, resolved = null;
    mgr.GetAll3(ref names, ref types, ref values, ref resolved);
    var nameArr = (string[])names;
    var valArr = (string[])resolved;
    for (int i = 0; i < nameArr.Length; i++)
        Console.WriteLine($"{nameArr[i]} = {valArr[i]}");

    // Write / update a property
    mgr.Add3("Project", (int)swCustomInfoType_e.swCustomInfoText,
        "MFG-2026-001", (int)swCustomPropertyAddOption_e.swCustomPropertyReplaceValue);

    // Read config-specific property
    var cfgMgr = ext.CustomPropertyManager["Default"];
    string valOut = "", resolvedOut = "";
    bool wasResolved;
    cfgMgr.Get6("Weight", false, out valOut, out resolvedOut, out wasResolved, out _);
}

How It Works

SolidWorks stores custom properties at two levels:

File-level properties: Accessed with an empty string as the configuration name
Configuration-specific properties: Accessed by passing the configuration name

The CustomPropertyManager provides methods to read, add, update, and delete properties:

GetAll3() reads all properties at once — returns parallel arrays of names, types, values, and resolved values
Add3() creates or updates a property — use the ReplaceValue option to overwrite existing ones
Get6() reads a single property by name — returns both the expression and the resolved (evaluated) value

Configuration-Specific vs File-Level

File-level properties appear on the Summary tab in SolidWorks — use these for part numbers, descriptions, and project metadata
Configuration-specific properties store values that change per config — weight, material, finish, etc.
When reading properties for a BOM, SolidWorks resolves config-specific first, then falls back to file-level

Tips

Always use Get6() (not Get5()) in modern SolidWorks versions — older methods are deprecated
The resolved value evaluates expressions like '"SW-Mass"' into actual mass values
For bulk reading without opening files, consider the Document Manager API — it reads properties without launching SolidWorks
Custom properties are case-insensitive — 'PartNumber' and 'PARTNUMBER' are the same property

SolidWorks APIC#Custom PropertiesMetadata