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Birupakhya Dash
Birupakhya Dash

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Fixing the "String or Binary Data Would Be Truncated" Error in EF Core

#efcore #dotnet #entityframework

Fixing the "String or Binary Data Would Be Truncated" Error in EF Core

If you’ve worked with Entity Framework Core and SQL Server, you’ve likely encountered this error:

String or binary data would be truncated
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At first glance, this error is frustrating because it doesn't tell you:

  • Which table failed
  • Which column caused the issue
  • What the allowed size is
  • What value exceeded the limit

So debugging becomes time-consuming.

The Problem

Consider this table:

Users
FirstName VARCHAR(20)
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Now insert:

"ThisIsAVeryLongNameThatExceedsLimit"
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SQL Server throws:

String or binary data would be truncated
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But gives no details.

The Solution: DBGuard

To solve this, I built a library called DBGuard.

DBGuard validates entity data against the actual database schema before SaveChanges.

How It Works

Flow:

Application
→ EF Core SaveChanges
→ DBGuard Interceptor
→ Validation Engine
→ Database

Example

Instead of SQL Server error:

String or binary data would be truncated
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DBGuard returns:

DBGuard Validation Failed

Table: Users
Column: FirstName
Allowed Length: 20
Actual Length: 45

Suggestion: Trim input or increase column length
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Installation 

dotnet add package DBGuard
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Usage 

builder.Services.AddDbGuard(connectionString);

builder.Services.AddDbContext<AppDbContext>((sp, options) =>
{
    var interceptor = sp.GetRequiredService<DbGuardInterceptor>();

    options.UseSqlServer(connectionString)
           .AddInterceptors(interceptor);
});
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Features

  • Schema-aware validation
  • Column length validation
  • Null & type validation
  • Decimal precision validation
  • EF Core interceptor
  • Logging and diagnostics

GitHub

https://github.com/birupakhya2000/DBGuard

Final Thoughts

This is a common problem many developers face.

I’d love feedback and suggestions from the community 🙌

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