Excel Limitation Regarding Data Validation for Strings

Curtis Chau

更新日期:8月 19, 2025

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View the article in English

Microsoft Excel 對於字串列表的長度有一個已知的限制，指出列表的總長度（包括像逗號這樣的分隔符）不能超過 255 個字元。

當您手動輸入字串列表到來源欄位，而不是從 Excel 工作表中已存在的範圍中選擇數據時，會出現這個問題，如下所示。

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Excel Limitation Issue

Excel 限制的解決方案

此限制的標準解決方法是將值列表創建在工作表的一列或一行內，而不是在來源欄位中輸入字串列表。如下面所示。

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Example Excel Limitation Solution

之後，使用數據驗證中的公式引用，例如 C1:C100，並指向該範圍。

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此方法繞過了限制，允許您創建不受 255 字元限制的下拉列表。

IronXL 的問題

IronXL 使用方法 AddStringListRule 來應用字串列表進行數據驗證。然而，由於上述 Excel 的相同字元限制，儲存方法仍然有效。不過，重要的是要注意，如果列表超過 255 字元，可能會導致一個嚴重問題：當文件被打開時，Excel 會崩潰。以下是說明此問題的示例。

using IronXL;
using IronXL.DataValidations;

// Set your license key here if you have one
IronXL.License.LicenseKey = "YOUR-LICENSE-KEY";
var workBook = WorkBook.Create(ExcelFileFormat.XLSX);

var sheet = workBook.CreateWorkSheet("Validation Rule Example using");
// Apply rules from row 2 down to row 500
var validationRangeStart = "2";
var validationRangeFinish = "500";

// --- 1. Define All Column Headers ---
sheet["A1"].Value = "String List Test";
sheet["B1"].Value = "Formula List Test";
sheet["A1:B1"].Style.Font.Bold = true;

// 256
string[] arrayString = new string[]
{
    "SKU-A01-R", "SKU-A02-R", "SKU-A03-R", "SKU-A04-R", "SKU-A05-R",
    "SKU-B01-G", "SKU-B02-G", "SKU-B03-G", "SKU-B04-G", "SKU-B05-G",
    "SKU-C01-B", "SKU-C02-B", "SKU-C03-B", "SKU-C04-B", "SKU-C05-B",
    "SKU-D01-Y", "SKU-D02-Y", "SKU-D03-Y", "SKU-D04-Y", "SKU-D05-Y",
    "END-001", "END-002", "END-003", "END-004", "END-005", "END-010", "END-001"
}; // total char with seperator 257 (230 char + 26 sperator [,] )

// no problem when write to a file
var skuValidation = sheet.DataValidations.AddStringListRule(sheet[$"A{validationRangeStart}:A{validationRangeFinish}"].RangeAddress, arrayString);

// set error box
skuValidation.ShowErrorBox = true;
skuValidation.ErrorBoxTitle = "Invalid SKU";
skuValidation.ErrorBoxText = "Please select a SKU from the list.";
skuValidation.ErrorAlert = ErrorAlert.Stop;

//attempt to save the file
var fileName = "CategoryProductCatalog.xlsx";
workBook.SaveAs(fileName);

using IronXL;
using IronXL.DataValidations;

// Set your license key here if you have one
IronXL.License.LicenseKey = "YOUR-LICENSE-KEY";
var workBook = WorkBook.Create(ExcelFileFormat.XLSX);

var sheet = workBook.CreateWorkSheet("Validation Rule Example using");
// Apply rules from row 2 down to row 500
var validationRangeStart = "2";
var validationRangeFinish = "500";

// --- 1. Define All Column Headers ---
sheet["A1"].Value = "String List Test";
sheet["B1"].Value = "Formula List Test";
sheet["A1:B1"].Style.Font.Bold = true;

// 256
string[] arrayString = new string[]
{
    "SKU-A01-R", "SKU-A02-R", "SKU-A03-R", "SKU-A04-R", "SKU-A05-R",
    "SKU-B01-G", "SKU-B02-G", "SKU-B03-G", "SKU-B04-G", "SKU-B05-G",
    "SKU-C01-B", "SKU-C02-B", "SKU-C03-B", "SKU-C04-B", "SKU-C05-B",
    "SKU-D01-Y", "SKU-D02-Y", "SKU-D03-Y", "SKU-D04-Y", "SKU-D05-Y",
    "END-001", "END-002", "END-003", "END-004", "END-005", "END-010", "END-001"
}; // total char with seperator 257 (230 char + 26 sperator [,] )

// no problem when write to a file
var skuValidation = sheet.DataValidations.AddStringListRule(sheet[$"A{validationRangeStart}:A{validationRangeFinish}"].RangeAddress, arrayString);

// set error box
skuValidation.ShowErrorBox = true;
skuValidation.ErrorBoxTitle = "Invalid SKU";
skuValidation.ErrorBoxText = "Please select a SKU from the list.";
skuValidation.ErrorAlert = ErrorAlert.Stop;

//attempt to save the file
var fileName = "CategoryProductCatalog.xlsx";
workBook.SaveAs(fileName);

Imports IronXL
Imports IronXL.DataValidations

' Set your license key here if you have one
IronXL.License.LicenseKey = "YOUR-LICENSE-KEY"
Dim workBook = WorkBook.Create(ExcelFileFormat.XLSX)

Dim sheet = workBook.CreateWorkSheet("Validation Rule Example using")
' Apply rules from row 2 down to row 500
Dim validationRangeStart = "2"
Dim validationRangeFinish = "500"

' --- 1. Define All Column Headers ---
sheet("A1").Value = "String List Test"
sheet("B1").Value = "Formula List Test"
sheet("A1:B1").Style.Font.Bold = True

' 256
Dim arrayString() As String = { "SKU-A01-R", "SKU-A02-R", "SKU-A03-R", "SKU-A04-R", "SKU-A05-R", "SKU-B01-G", "SKU-B02-G", "SKU-B03-G", "SKU-B04-G", "SKU-B05-G", "SKU-C01-B", "SKU-C02-B", "SKU-C03-B", "SKU-C04-B", "SKU-C05-B", "SKU-D01-Y", "SKU-D02-Y", "SKU-D03-Y", "SKU-D04-Y", "SKU-D05-Y", "END-001", "END-002", "END-003", "END-004", "END-005", "END-010", "END-001" }

' no problem when write to a file
Dim skuValidation = sheet.DataValidations.AddStringListRule(sheet($"A{validationRangeStart}:A{validationRangeFinish}").RangeAddress, arrayString)

' set error box
skuValidation.ShowErrorBox = True
skuValidation.ErrorBoxTitle = "Invalid SKU"
skuValidation.ErrorBoxText = "Please select a SKU from the list."
skuValidation.ErrorAlert = ErrorAlert.Stop

'attempt to save the file
Dim fileName = "CategoryProductCatalog.xlsx"
workBook.SaveAs(fileName)

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在代碼中，我們嘗試將名為 arrayString 的字串列表作為字串列表的來源來創建下拉列表。然後我們嘗試將其儲存為 CategoryProductCatalog.xlsx。但是，由於這些限制，當用 Microsoft Excel 開啟文件時，它會顯示一條訊息，指出文件已損壞且無法打開。

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IronXL 的解決方案

為了解決這個 Excel 限制，IronXL 提供了 AddFormulaListRule 方法，該方法在 DataValidations 屬性中可用。該方法類似於處理 Excel 的解決方案。

我們首先將值列表寫入工作表中的一個範圍單元格中。然後使用 AddFormulaListRule 引用該範圍作為下拉列表的來源。通過我們對 Excel 解決方案所做的相同方法來有效地繞過限制，但在此實例中，它是程序化的。

正確使用 AddFormulaListRule 不僅繞過了 Excel 限制，還確保了文件在 Excel 中打開時仍然可讀和穩定，即使有長長的數值列表。

代碼示例

下面是繞過此問題的附加示例代碼。使用相同的工作簿，我們首先創建一個工作表，然後定義所有的列標題。我們輸入了前一個示例中的字串列表以及新數據以演示該功能。然後我們用上述的驗證範圍調用 AddFormulaListRule。最後，我們將其儲存為 validationRuleExample.xlsx。為了確保我們的工作簿不會損壞並能正常使用，我們在 Excel 中開啟它。這一步是至關重要的，因為它證明了我們的代碼成功實施。

using IronXL;
using IronXL.DataValidations;
using System;

// Set your license key here if you have one
IronXL.License.LicenseKey = "YOUR-LICENSE-KEY";
var workBook = WorkBook.Create(ExcelFileFormat.XLSX);

var sheet = workBook.CreateWorkSheet("Validation Rule Example using");
// Apply rules from row 2 down to row 500
var validationRangeStart = "2";
var validationRangeFinish = "500";

// --- 1. Define All Column Headers ---
sheet["A1"].Value = "String List Test";
sheet["B1"].Value = "Formula List Test";
sheet["A1:B1"].Style.Font.Bold = true;

string[] arrayString2 = new string[] 
{ 
    "SKU-A01-R", "SKU-A02-R", "SKU-A03-R", "SKU-A04-R", "SKU-A05-R",
    "SKU-B01-G", "SKU-B02-G", "SKU-B03-G", "SKU-B04-G", "SKU-B05-G",
    "SKU-C01-B", "SKU-C02-B", "SKU-C03-B", "SKU-C04-B", "SKU-C05-B",
    "SKU-D01-Y", "SKU-D02-Y", "SKU-D03-Y", "SKU-D04-Y", "SKU-D05-Y",
    "END-001", "END-002", "END-003", "END-004", "END-005", "END-010", "END-001",
    "IRON01","IRON02","IRON03","IRON04","IRON05","IRON06","IRON07","IRON08","IRON09","IRON10",
    "IRON11","IRON12","IRON13","IRON14","IRON15","IRON16","IRON17","IRON18","IRON19","IRON20",
    "IRON21","IRON22","IRON23","IRON24","IRON25","IRON26","IRON27","IRON28","IRON29","IRON30",
    "IRON31","IRON32","IRON33","IRON34","IRON35","IRON36","IRON37","IRON38","IRON39","IRON40",
    "IRON41","IRON42","IRON43","IRON44","IRON45","IRON46","IRON47","IRON48","IRON49","IRON50",
    "IRON51","IRON52","IRON53","IRON54","IRON55","IRON56","IRON57","IRON58","IRON59","IRON60",
    "IRON61","IRON62","IRON63","IRON64","IRON65","IRON66","IRON67","IRON68","IRON69","IRON70",
    "IRON71","IRON72","IRON73","IRON74","IRON75","IRON76","IRON77","IRON78","IRON79","IRON80",
    "IRON81","IRON82","IRON83","IRON84","IRON85","IRON86","IRON87","IRON88","IRON89","IRON90",
    "IRON91","IRON92","IRON93","IRON94","IRON95","IRON96","IRON97","IRON98","IRON99","IRON100"
}; // total char with seperator 257 (230 char + 26 sperator [,] )

//Write the contents of your array to column A of the data sheet.
for (int i = 0; i < arrayString2.Length; i++)
{
    // Note: IronXL row and cell indices are 1-based.
    sheet[$"A{i + 1}"].Value = arrayString2[i];
}

// Create the formula string that points to our data range.
// This will look like: 'ValidationData'!$A$1:$A$100

string formula = $"'{sheet.Name}'!$A$1:$A${arrayString2.Length}";
Console.WriteLine($"Generated formula for validation: {formula}");

var sku2Validation = sheet.DataValidations.AddFormulaListRule(sheet[$"B{validationRangeStart}:B{validationRangeFinish}"], formula);

sku2Validation.ShowErrorBox = true;
sku2Validation.ErrorBoxTitle = "Invalid SKU2";
sku2Validation.ErrorBoxText = "Please select a SKU from the list.";
sku2Validation.ErrorAlert = ErrorAlert.Stop;

// --- Final Touches ---
sheet.AutoSizeColumn(0, true);
sheet.AutoSizeColumn(1, true);

var fileName = "validationRuleExample.xlsx";
workBook.SaveAs(fileName);

Console.WriteLine($"Successfully created '{fileName}' with 2 validation rules example.");

using IronXL;
using IronXL.DataValidations;
using System;

// Set your license key here if you have one
IronXL.License.LicenseKey = "YOUR-LICENSE-KEY";
var workBook = WorkBook.Create(ExcelFileFormat.XLSX);

var sheet = workBook.CreateWorkSheet("Validation Rule Example using");
// Apply rules from row 2 down to row 500
var validationRangeStart = "2";
var validationRangeFinish = "500";

// --- 1. Define All Column Headers ---
sheet["A1"].Value = "String List Test";
sheet["B1"].Value = "Formula List Test";
sheet["A1:B1"].Style.Font.Bold = true;

string[] arrayString2 = new string[] 
{ 
    "SKU-A01-R", "SKU-A02-R", "SKU-A03-R", "SKU-A04-R", "SKU-A05-R",
    "SKU-B01-G", "SKU-B02-G", "SKU-B03-G", "SKU-B04-G", "SKU-B05-G",
    "SKU-C01-B", "SKU-C02-B", "SKU-C03-B", "SKU-C04-B", "SKU-C05-B",
    "SKU-D01-Y", "SKU-D02-Y", "SKU-D03-Y", "SKU-D04-Y", "SKU-D05-Y",
    "END-001", "END-002", "END-003", "END-004", "END-005", "END-010", "END-001",
    "IRON01","IRON02","IRON03","IRON04","IRON05","IRON06","IRON07","IRON08","IRON09","IRON10",
    "IRON11","IRON12","IRON13","IRON14","IRON15","IRON16","IRON17","IRON18","IRON19","IRON20",
    "IRON21","IRON22","IRON23","IRON24","IRON25","IRON26","IRON27","IRON28","IRON29","IRON30",
    "IRON31","IRON32","IRON33","IRON34","IRON35","IRON36","IRON37","IRON38","IRON39","IRON40",
    "IRON41","IRON42","IRON43","IRON44","IRON45","IRON46","IRON47","IRON48","IRON49","IRON50",
    "IRON51","IRON52","IRON53","IRON54","IRON55","IRON56","IRON57","IRON58","IRON59","IRON60",
    "IRON61","IRON62","IRON63","IRON64","IRON65","IRON66","IRON67","IRON68","IRON69","IRON70",
    "IRON71","IRON72","IRON73","IRON74","IRON75","IRON76","IRON77","IRON78","IRON79","IRON80",
    "IRON81","IRON82","IRON83","IRON84","IRON85","IRON86","IRON87","IRON88","IRON89","IRON90",
    "IRON91","IRON92","IRON93","IRON94","IRON95","IRON96","IRON97","IRON98","IRON99","IRON100"
}; // total char with seperator 257 (230 char + 26 sperator [,] )

//Write the contents of your array to column A of the data sheet.
for (int i = 0; i < arrayString2.Length; i++)
{
    // Note: IronXL row and cell indices are 1-based.
    sheet[$"A{i + 1}"].Value = arrayString2[i];
}

// Create the formula string that points to our data range.
// This will look like: 'ValidationData'!$A$1:$A$100

string formula = $"'{sheet.Name}'!$A$1:$A${arrayString2.Length}";
Console.WriteLine($"Generated formula for validation: {formula}");

var sku2Validation = sheet.DataValidations.AddFormulaListRule(sheet[$"B{validationRangeStart}:B{validationRangeFinish}"], formula);

sku2Validation.ShowErrorBox = true;
sku2Validation.ErrorBoxTitle = "Invalid SKU2";
sku2Validation.ErrorBoxText = "Please select a SKU from the list.";
sku2Validation.ErrorAlert = ErrorAlert.Stop;

// --- Final Touches ---
sheet.AutoSizeColumn(0, true);
sheet.AutoSizeColumn(1, true);

var fileName = "validationRuleExample.xlsx";
workBook.SaveAs(fileName);

Console.WriteLine($"Successfully created '{fileName}' with 2 validation rules example.");

Imports IronXL
Imports IronXL.DataValidations
Imports System

' Set your license key here if you have one
IronXL.License.LicenseKey = "YOUR-LICENSE-KEY"
Dim workBook = WorkBook.Create(ExcelFileFormat.XLSX)

Dim sheet = workBook.CreateWorkSheet("Validation Rule Example using")
' Apply rules from row 2 down to row 500
Dim validationRangeStart = "2"
Dim validationRangeFinish = "500"

' --- 1. Define All Column Headers ---
sheet("A1").Value = "String List Test"
sheet("B1").Value = "Formula List Test"
sheet("A1:B1").Style.Font.Bold = True

Dim arrayString2() As String = {"SKU-A01-R", "SKU-A02-R", "SKU-A03-R", "SKU-A04-R", "SKU-A05-R", "SKU-B01-G", "SKU-B02-G", "SKU-B03-G", "SKU-B04-G", "SKU-B05-G", "SKU-C01-B", "SKU-C02-B", "SKU-C03-B", "SKU-C04-B", "SKU-C05-B", "SKU-D01-Y", "SKU-D02-Y", "SKU-D03-Y", "SKU-D04-Y", "SKU-D05-Y", "END-001", "END-002", "END-003", "END-004", "END-005", "END-010", "END-001", "IRON01", "IRON02", "IRON03", "IRON04", "IRON05", "IRON06", "IRON07", "IRON08", "IRON09", "IRON10", "IRON11", "IRON12", "IRON13", "IRON14", "IRON15", "IRON16", "IRON17", "IRON18", "IRON19", "IRON20", "IRON21", "IRON22", "IRON23", "IRON24", "IRON25", "IRON26", "IRON27", "IRON28", "IRON29", "IRON30", "IRON31", "IRON32", "IRON33", "IRON34", "IRON35", "IRON36", "IRON37", "IRON38", "IRON39", "IRON40", "IRON41", "IRON42", "IRON43", "IRON44", "IRON45", "IRON46", "IRON47", "IRON48", "IRON49", "IRON50", "IRON51", "IRON52", "IRON53", "IRON54", "IRON55", "IRON56", "IRON57", "IRON58", "IRON59", "IRON60", "IRON61", "IRON62", "IRON63", "IRON64", "IRON65", "IRON66", "IRON67", "IRON68", "IRON69", "IRON70", "IRON71", "IRON72", "IRON73", "IRON74", "IRON75", "IRON76", "IRON77", "IRON78", "IRON79", "IRON80", "IRON81", "IRON82", "IRON83", "IRON84", "IRON85", "IRON86", "IRON87", "IRON88", "IRON89", "IRON90", "IRON91", "IRON92", "IRON93", "IRON94", "IRON95", "IRON96", "IRON97", "IRON98", "IRON99", "IRON100"}

'Write the contents of your array to column A of the data sheet.
For i As Integer = 0 To arrayString2.Length - 1
	' Note: IronXL row and cell indices are 1-based.
	sheet($"A{i + 1}").Value = arrayString2(i)
Next i

' Create the formula string that points to our data range.
' This will look like: 'ValidationData'!$A$1:$A$100

Dim formula As String = $"'{sheet.Name}'!$A$1:$A${arrayString2.Length}"
Console.WriteLine($"Generated formula for validation: {formula}")

Dim sku2Validation = sheet.DataValidations.AddFormulaListRule(sheet($"B{validationRangeStart}:B{validationRangeFinish}"), formula)

sku2Validation.ShowErrorBox = True
sku2Validation.ErrorBoxTitle = "Invalid SKU2"
sku2Validation.ErrorBoxText = "Please select a SKU from the list."
sku2Validation.ErrorAlert = ErrorAlert.Stop

' --- Final Touches ---
sheet.AutoSizeColumn(0, True)
sheet.AutoSizeColumn(1, True)

Dim fileName = "validationRuleExample.xlsx"
workBook.SaveAs(fileName)

Console.WriteLine($"Successfully created '{fileName}' with 2 validation rules example.")

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