c# compiler says array is NULL but array was instantiated with NEW in constructor

Question

This is an array class that let the user choose the type of array ( string or int ). Am new to c# but am familiar with OOP, i didn't understand why i got this error

System.NullReferenceException: 'Object reference not set to an instance of an object.' mArr was null.

I have allocated memory for array of ( int[] type or string[] type ) based on " check " variable, so the array is there, it's not Null to my understanding. I choosed "int" just to test code.

problem on line 52.

1 using System;
2 public class TP1
3 {
4     public static void Main() 
5     {
6         tableau tab = new tableau(10, "int");
7         tab.fillTab();
8         tab.printTab();
9     }
10      public class tableau
11     {
12         public
13         int mLength;
14         string mType;
15         int tmp;
16         string tmp2;
17         int[] mArr;
18         string[] mArr2;
19         int check;
20         public tableau(int n, string type)                             
21         {
22                 this.mLength = n;
23                 this.mType = type;
24                 if (mType == "int")                           
25                 {
26                     check = 1;
27                     int[] mArr = new int[mLength];               
28             }
29                 else if (mType == "string")                  
30                 {
31                     check = 2;
32                     string[] mArr2 = new string[mLength];
33                 }
34         }
35         public int getLength()
36         {
37             return mLength;
38         }
39         public string getType()
40         {
41             return mType;
42         }
43         public void fillTab()
44         {
45             if (check == 1)                                 
46             {
47                 Console.WriteLine("Entrez les valeurs de type int : ");
48                 int i;
49                 for (i = 0; i < getLength(); i++)
50                 {
51                     Console.WriteLine("Entrez la valeur {0}: ", i + 1);
52                     mArr[i] = Convert.ToInt32(Console.ReadLine());         //Problem here
53                 }
54 
55             }
56             if (check == 2)                                "
57             {
58                 Console.WriteLine("Entrez les valeurs de type string : ");
59                 int i;
60                 for (i = 0; i < getLength(); i++)
61                 {
62                     Console.WriteLine("Entrez la chaine {0]: ", i + 1);
63                     mArr2[i] = Console.ReadLine();
64                 }
65             }
66         }
67         public void sort()
68         {
69             if (check == 1)
70             {
71 
72                 for (int i = 0; i < getLength(); i++)
73                 {
74                     for (int j = i + 1; j < getLength(); j++)
75                     {
76                         if (mArr[j] < mArr[i])
77                         {
78                             tmp = mArr[i];
79                             mArr[i] = mArr[j];
80                             mArr[j] = tmp;
81                         }
82                     }
83                 }
84             }
85             else if (check == 2)
86             {
87                 for (int i = 0; i < getLength(); i++)
88                 {
89                     string temp = mArr2[i];
90                     for (int j = i + 1; j < getLength(); j++)
91                     {
92                         string temp2 = mArr2[j];
93                         if (string.Compare(temp, temp2) == 1)
94                         {
95                             tmp2 = mArr2[i];
96                             mArr2[i] = mArr2[j];
97                             mArr2[j] = tmp2;
98                         }
99                     }
100                 }
101             }
102         }
103         public void printTab()
104         {
105             if (check == 1)
106             {
107 
108                 Console.WriteLine("\nTableau trié aprés insertion :");
109                 for (int i = 0; i < mLength; i++)
110                 {
111                     Console.Write("{0}  ", mArr[i]);
112                 }
113             }
114             if (check == 2)
115             {
116 
117                 Console.WriteLine("\nTableau trié aprés insertion :");
118                 for (int i = 0; i < mLength; i++)
119                 {
120                     Console.Write("{0}  ", mArr2[i]);
121                 }
122             }
123         }
124     }
125 }