Call GetConstructor to get the constructor
using System; using System.Text; using System.Reflection; class MainClass { public static StringBuilder CreateStringBuilder() { Type type = typeof(StringBuilder); Type[] argTypes = new Type[] { typeof(System.String), typeof(System.Int32) }; ConstructorInfo cInfo = type.GetConstructor(argTypes); object[] argVals = new object[] { "Some string", 30 }; StringBuilder sb = (StringBuilder)cInfo.Invoke(argVals); return sb; } }