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POHow to add only an attribute on a class at runtime?
 

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  1. POHow to add only an attribute on a class at runtime?
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    <p>I managed to create this class at run time with Reflection Emit:</p> <pre><code>[DelimitedRecord(",")] public partial class Person { [FieldOrder(0)] private string firstName; [FieldOrder(1)] private string lastName; public string FirstName { get { return firstName; } set { firstName = value; } } public string LastName { get { return lastName; } set { lastName = value; } } } </code></pre> <p>like this:</p> <pre><code> //create the builder AssemblyName assembly = new AssemblyName("FileHelpersTests"); AppDomain appDomain = System.Threading.Thread.GetDomain(); AssemblyBuilder assemblyBuilder = appDomain.DefineDynamicAssembly(assembly, AssemblyBuilderAccess.Run); ModuleBuilder moduleBuilder = assemblyBuilder.DefineDynamicModule(assembly.Name); //create the class TypeBuilder typeBuilder = moduleBuilder.DefineType("Person", TypeAttributes.Public | TypeAttributes.AutoClass | TypeAttributes.AnsiClass | TypeAttributes.BeforeFieldInit, typeof(System.Object)); //create the Delimiter attribute Type[] delimiterAttributeParams = new Type[] { typeof(string) }; ConstructorInfo delimiterAttrInfo = typeof(DelimitedRecordAttribute).GetConstructor(delimiterAttributeParams); CustomAttributeBuilder delimiterAttributeBuilder = new CustomAttributeBuilder(delimiterAttrInfo, new object[] { ";" }); typeBuilder.SetCustomAttribute(delimiterAttributeBuilder); //create the firstName field FieldBuilder firstNameField = typeBuilder.DefineField("firstName", typeof(System.String), FieldAttributes.Private); //create the firstName attribute [FieldOrder(0)] Type[] firstNameFieldOrderAttributeParams = new Type[] { typeof(int) }; ConstructorInfo firstNameFieldOrderAttrInfo = typeof(FieldOrderAttribute).GetConstructor(firstNameFieldOrderAttributeParams); CustomAttributeBuilder firstNameFieldOrderAttributeBuilder = new CustomAttributeBuilder(firstNameFieldOrderAttrInfo, new object[] { 0 }); firstNameField.SetCustomAttribute(firstNameFieldOrderAttributeBuilder); //create the FirstName property PropertyBuilder firstNameProperty = typeBuilder.DefineProperty("FirstName", PropertyAttributes.HasDefault, typeof(System.String), null); //create the FirstName Getter MethodBuilder firstNamePropertyGetter = typeBuilder.DefineMethod("get_FirstName", MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, typeof(System.String), Type.EmptyTypes); ILGenerator firstNamePropertyGetterIL = firstNamePropertyGetter.GetILGenerator(); firstNamePropertyGetterIL.Emit(OpCodes.Ldarg_0); firstNamePropertyGetterIL.Emit(OpCodes.Ldfld, firstNameField); firstNamePropertyGetterIL.Emit(OpCodes.Ret); //create the FirstName Setter MethodBuilder firstNamePropertySetter = typeBuilder.DefineMethod("set_FirstName", MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, null, new Type[] { typeof(System.String) }); ILGenerator firstNamePropertySetterIL = firstNamePropertySetter.GetILGenerator(); firstNamePropertySetterIL.Emit(OpCodes.Ldarg_0); firstNamePropertySetterIL.Emit(OpCodes.Ldarg_1); firstNamePropertySetterIL.Emit(OpCodes.Stfld, firstNameField); firstNamePropertySetterIL.Emit(OpCodes.Ret); //assign getter and setter firstNameProperty.SetGetMethod(firstNamePropertyGetter); firstNameProperty.SetSetMethod(firstNamePropertySetter); //create the lastName field FieldBuilder lastNameField = typeBuilder.DefineField("lastName", typeof(System.String), FieldAttributes.Private); //create the lastName attribute [FieldOrder(1)] Type[] lastNameFieldOrderAttributeParams = new Type[] { typeof(int) }; ConstructorInfo lastNameFieldOrderAttrInfo = typeof(FieldOrderAttribute).GetConstructor(lastNameFieldOrderAttributeParams); CustomAttributeBuilder lastNameFieldOrderAttributeBuilder = new CustomAttributeBuilder(lastNameFieldOrderAttrInfo, new object[] { 1 }); lastNameField.SetCustomAttribute(lastNameFieldOrderAttributeBuilder); //create the LastName property PropertyBuilder lastNameProperty = typeBuilder.DefineProperty("LastName", PropertyAttributes.HasDefault, typeof(System.String), null); //create the LastName Getter MethodBuilder lastNamePropertyGetter = typeBuilder.DefineMethod("get_LastName", MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, typeof(System.String), Type.EmptyTypes); ILGenerator lastNamePropertyGetterIL = lastNamePropertyGetter.GetILGenerator(); lastNamePropertyGetterIL.Emit(OpCodes.Ldarg_0); lastNamePropertyGetterIL.Emit(OpCodes.Ldfld, lastNameField); lastNamePropertyGetterIL.Emit(OpCodes.Ret); //create the FirstName Setter MethodBuilder lastNamePropertySetter = typeBuilder.DefineMethod("set_FirstName", MethodAttributes.Public | MethodAttributes.SpecialName | MethodAttributes.HideBySig, null, new Type[] { typeof(System.String) }); ILGenerator lastNamePropertySetterIL = lastNamePropertySetter.GetILGenerator(); lastNamePropertySetterIL.Emit(OpCodes.Ldarg_0); lastNamePropertySetterIL.Emit(OpCodes.Ldarg_1); lastNamePropertySetterIL.Emit(OpCodes.Stfld, lastNameField); lastNamePropertySetterIL.Emit(OpCodes.Ret); //assign getter and setter lastNameProperty.SetGetMethod(lastNamePropertyGetter); lastNameProperty.SetSetMethod(lastNamePropertySetter); </code></pre> <p>What i would really like is to declare my class like this:</p> <pre><code> public partial class Person { private string firstName; private string lastName; public string FirstName { get { return firstName; } set { firstName = value; } } public string LastName { get { return lastName; } set { lastName = value; } } } </code></pre> <p>and at run time only add those attributes. For the first name field i am thinking at something like this</p> <pre><code> //get the builder to that field FieldBuilder firstNameField = //create the attribute [FieldOrder(0)] Type[] firstNameFieldOrderAttributeParams = new Type[] { typeof(int) }; ConstructorInfo firstNameFieldOrderAttrInfo = typeof(FieldOrderAttribute).GetConstructor(firstNameFieldOrderAttributeParams); CustomAttributeBuilder firstNameFieldOrderAttributeBuilder = new CustomAttributeBuilder(firstNameFieldOrderAttrInfo, new object[] { 0 }); firstNameField.SetCustomAttribute(firstNameFieldOrderAttributeBuilder); </code></pre> <p>How to get the builder to that field?</p>
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    1. PO
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    1. PTQuestion
    1. This table or related slice is empty.
    1. USgigi
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    1. This table or related slice is empty.
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    1. PO
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    1. VO
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      1. POHow to add only an attribute on a class at runtime?
      1. USHamlet Hakobyan
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    2. VO
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      1. POHow to add only an attribute on a class at runtime?
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      1. VTUpMod
    3. VO
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      1. POHow to add only an attribute on a class at runtime?
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    1. COYou cannot add attribute at runtime to an existing class. Attribute are meant to be metadata.
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      1. POHow to add only an attribute on a class at runtime?
      1. USrpgmaker
    2. COSo, it is possible to create a whole class with attributes but it is impossible to add just the attributes?
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      1. POHow to add only an attribute on a class at runtime?
      1. USgigi
    3. COThat is correct. The attribute metadata are embedded within your compiled code are cannot be changed. Generating a new class on the fly that inherit from it and do whatever you want is the best option
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      1. POHow to add only an attribute on a class at runtime?
      1. USrpgmaker
 

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