Why Do I Get a 'Use of Unassigned Local Variable' Error, and How Can I Fix It?

Understanding the "Use of unassigned local variable" error

The "Use of unassigned local variable" error occurs when a variable is used but not assigned a value. In the provided code, it refers to the variables annualRate, monthlyCharge, and lateFee.

The compiler issues this error because it expects all local variables to be initialized or assigned before use. However, in the provided code, any of the creditPlan conditions in the credit plan (if) determination may not be met. As a result, variables annualRate, monthlyCharge and lateFee remain unassigned.

Solve the problem

To resolve this error, we need to ensure that these variables are assigned a value in all possible cases. This can be achieved by using the else block or the switch statement:

Use else block

<code class="language-c#">if (creditPlan == "0")
{
    // ...
}
else if (creditPlan == "1")
{
    // ...
}
else if (creditPlan == "2")
{
    // ...
}
else
{
    // 当 creditPlan 未指定时的默认值
    annualRate = 0.15; // 15%
    lateFee = 0.00;
    monthlyCharge = 0.00;
}</code>

Use the switch statement

<code class="language-c#">switch (creditPlan)
{
    case "0":
        // ...
        break;
    case "1":
        // ...
        break;
    case "2":
        // ...
        break;
    default:
        // 当 creditPlan 未指定时的默认值
        annualRate = 0.15; // 15%
        lateFee = 0.00;
        monthlyCharge = 0.00;
        break;
}</code>

By ensuring that these variables are assigned a value in all cases, the compiler can correctly identify and prevent the use of unassigned local variables. This results in more robust and bug-free code.

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