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How to Resolve Error "CS0543: 'enumeration' : the enumerator value is too large to fit in its type" in C#

The Compiler Error CS0543 is a range overflow error specific to Enums. The message reads: "'EnumName' : the enumerator value is too large to fit in its type".

In C#, an enum is backed by an integral type (by default, int). This means every member of the enum must map to a number that fits within the range of that backing type. If you try to assign a value (like 3,000,000,000) that exceeds the maximum limit of the underlying type (e.g., int.MaxValue is 2,147,483,647), the compiler raises CS0543.

This guide explains how to change the backing type of an enum to accommodate larger values.

Understanding Enum Backing Types​

Unless specified otherwise, every enum in C# is treated as an int (System.Int32).

  • Default Range: -2,147,483,648 to 2,147,483,647.

If you need values outside this range, you must explicitly tell the compiler to use a larger container, such as uint (Unsigned Int) or long (Int64).

Supported Types: byte, sbyte, short, ushort, int, uint, long, ulong.

Scenario 1: Default Integer Overflow​

This is the most common cause. You assign a number larger than ~2.1 billion to a standard enum member.

Example of error​

public enum FileSize
{
    Empty = 0,
    Kilobyte = 1024,
    Megabyte = 1048576,
    
    // ⛔️ Error CS0543: 'Gigabyte' : the enumerator value is too large to fit in its type.
    // 3,000,000,000 is larger than int.MaxValue (2,147,483,647).
    LargeValue = 3000000000
}

Solution: Change to long or uint​

Change the underlying type by adding a colon : and the type keyword after the enum name.

// ✅ Correct: 'long' can hold values up to 9 quintillion.
public enum FileSize : long
{
    Empty = 0,
    Kilobyte = 1024,
    Megabyte = 1048576,
    LargeValue = 3000000000
}

Scenario 2: Overflowing Specific Types (byte/short)​

Sometimes developers explicitly choose a small type (like byte) to save memory, but then accidentally add a member that exceeds that small limit (e.g., 256 for a byte).

Example of error​

// Defined as 'byte' (Max value 255)
public enum HttpStatusCode : byte
{
    Ok = 200,
    
    // ⛔️ Error CS0543: 404 does not fit in a byte (0-255).
    NotFound = 404,
    InternalServerError = 500
}

Solution: Upgrade the Type​

Change the type to short (Max 32,767) or int (Default).

// ✅ Correct: 'short' (System.Int16) is sufficient for HTTP codes.
public enum HttpStatusCode : short
{
    Ok = 200,
    NotFound = 404,
    InternalServerError = 500
}

Scenario 3: Hexadecimal Literals and Flags​

When using [Flags] for bitmasks, it is common to use Hexadecimal (0x...). If you define a flag that uses the 32nd bit (the highest bit) in a signed int, it might be interpreted as a negative number or an overflow depending on how it's written.

Example of error​

[System.Flags]
public enum Permissions
{
    Read = 1,
    Write = 2,
    
    // ⛔️ Error CS0543: 0xFFFFFFFF is 4,294,967,295.
    // This fits in a 32-bit container, but it is too large for a SIGNED int.
    All = 0xFFFFFFFF 
}

Solution: Use uint​

Use an unsigned integer (uint) to allow the full 32-bit range without sign issues.

[System.Flags]
// ✅ Correct: 'uint' allows the full range of 0 to 4,294,967,295
public enum Permissions : uint
{
    Read = 1,
    Write = 2,
    All = 0xFFFFFFFF
}
note

Alternatively, you could cast the value to int using unchecked((int)0xFFFFFFFF), but changing the backing type is cleaner.

Conclusion​

CS0543 prevents data truncation in Enums.

  1. Check the Value: Is the number larger than 2.1 Billion?
  2. Check the Type: Did you restrict the enum to byte or short?
  3. The Fix: Expand the backing type using the syntax enum Name : NewType.

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