parameters validation by custom attributes in c#

Hello friend,

I try to use the attribute to verify the parameters of the client.

Now, how to use the interface injection to verify?

public interface ICheckParameter{

void Check(object objValue, string parameterName);

}

[AttributeUsage(AttributeTargets.Parameter)]

public class CheckIsNullOrEmptyAttribute : Attribute,ICheckParameter{

public CheckIsNullOrEmptyAttribute(){}
public void Check(object objValue,string parameterName){

if (objValue == null) throw new ArgumentNullException(parameterName);

}

}

[AttributeUsage(AttributeTargets.Parameter)]

public class CheckLengthAttribute : Attribute,ICheckParameter {

private int _minValue;
private int _maxValue;
public CheckLengthAttribute(int minValue,int maxValue){

this._minValue=minValue;
this._maxValue=maxValue;

}
public void Check(object objValue, string parameterName){

if (objValue == null) throw new ArgumentNullException(parameterName, "The object can't be null.");
int len = objValue.ToString().Length;
if (lenthis._maxValue)
throw new ArgumentOutOfRangeException(parameterName,
string.Format("The value length must be between {0} and {1}",
this._minValue,this._maxValue));

}

}

public interface ICheckPower{

void CheckPower([CheckIsNullOrEmpty]string uName, [CheckLength(6, 10)]string pwd);

}

public class LoginClass : ICheckPower {

public LoginClass() { }
public void CheckPower(string uName, string pwd) {

try{
Console.WriteLine("Pass...\n");
}
catch (Exception error)
{
Console.WriteLine("An Error:{0}\n",error.Message);
}

}

}

class Program {

static void Main(string[] args){
LoginClass lc = new LoginClass();
lc.CheckPower(null, "123456");
lc.CheckPower("Test", "123");
Console.ReadKey(true);
}

}

Thank. :)

Try this:

// add using directive

using System.Reflection;

// add some lines to CheckPower method

public class LoginClass : ICheckPower {

public LoginClass() { }

public void CheckPower(string uName, string pwd) {

Type t = typeof(ICheckPower);

MethodInfo mi = t.GetMethod("CheckPower");

ParameterInfo[] pia = mi.GetParameters();

object[] uNameAttribs = pia[0].GetCustomAttributes(false);

CheckIsNullOrEmptyAttribute cinoea = (CheckIsNullOrEmptyAttribute)uNameAttribs[0];

object[] pwdAttribs = pia[1].GetCustomAttributes(false);

CheckLengthAttribute cla = (CheckLengthAttribute)pwdAttribs[0];

try{

cinoea.Check(uName, "uName");

cla.Check(pwd, "pwd");

Console.WriteLine("Pass...\n");

}

catch (Exception error)

{

Console.WriteLine("An Error: {0}\n",error.Message);

}

}

The output now should be:

An Error: Value cannot be null.

Parameter name: uName

An Error: The value length must be between 6 and 10

Parameter name: pwd

2 Replies

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Vulpes11y ago
Accepted answer
Try this:

// add using directive

using System.Reflection;

// add some lines to CheckPower method

public class LoginClass : ICheckPower {
public LoginClass() { }
public void CheckPower(string uName, string pwd) {

Type t = typeof(ICheckPower);
MethodInfo mi = t.GetMethod("CheckPower");
ParameterInfo[] pia = mi.GetParameters();
object[] uNameAttribs = pia[0].GetCustomAttributes(false);
CheckIsNullOrEmptyAttribute cinoea = (CheckIsNullOrEmptyAttribute)uNameAttribs[0];
object[] pwdAttribs = pia[1].GetCustomAttributes(false);
CheckLengthAttribute cla = (CheckLengthAttribute)pwdAttribs[0];

try{
cinoea.Check(uName, "uName");
cla.Check(pwd, "pwd");
Console.WriteLine("Pass...\n");
}
catch (Exception error)
{
Console.WriteLine("An Error: {0}\n",error.Message);
}
}
}

The output now should be:

An Error: Value cannot be null.
Parameter name: uName

An Error: The value length must be between 6 and 10
Parameter name: pwd
Ken H11y ago
Thank for you. :)