ArcGIS Pro 2.7 API Reference Guide
Patches Property
Example 

ArcGIS.Core.Geometry Namespace > MultipatchBuilderEx Class : Patches Property
Gets or sets the list of patches for this instance.
Syntax
public IList<Patch> Patches {get; set;}
Public Property Patches As IList(Of Patch)
Remarks
The getter returns the reference to the list which can be modified directly. The setter copies the input IList to an internal container. Only the list is copied, not the patches. Note also, that the patches don't hold a reference to the containing multipatch builder. Therefore, changes made to the patches directly, such as adding a missing array of Ms to the patch, will not change the attribute awareness (HasM) of the builder.
Example
// create the multipatchBuilderEx object
var builder = new ArcGIS.Core.Geometry.MultipatchBuilderEx(multipatch);

// check some properties
bool hasM = builder.HasM;
bool hasZ = builder.HasZ;
bool hasID = builder.HasID;
bool isEmpty = builder.IsEmpty;
bool hasNormals = builder.HasNormals;

var patches = builder.Patches;
int patchCount = patches.Count;

// if there's some patches
if (patchCount > 0)
{
  int pointCount = builder.GetPatchPointCount(0);

  // replace the first point in the first patch
  if (pointCount > 0)
  {
    // get the first point
    var pt = builder.GetPoint(0, 0);
    builder.SetPoint(0, 0, newPoint);
  }

  // check which patches currently contain the texture
  var texture = builder.QueryPatchIndicesWithTexture(brickTextureResource);

  // assign a texture material
  patches[0].Material = brickMaterialTexture;
}

// update the builder for M awareness
builder.HasM = true;
// synchronize the patch attributes to match the builder attributes
//   in this instance because we just set HasM to true on the builder, each patch will now get a default M value for it's set of coordinates
builder.SynchronizeAttributeAwareness();

// call ToGeometry to get the multipatch
multipatch = builder.ToGeometry() as Multipatch;

// multipatch.HasM will be true
Requirements

Target Platforms: Windows 10, Windows 8.1

See Also

Reference

MultipatchBuilderEx Class
MultipatchBuilderEx Members